4y=x 3x-y=70

9 Answers | Add Yours

violy's profile pic

violy | High School Teacher | (Level 1) Associate Educator

Posted on

This can also be solve using Elimination Method.

Write the first equation in general form: ax + by + c.

Subtract both sides by 4y.

`4y - 4y = x - 4y`

`0 = x - 4y` or `x - 4y = 0`

Let us eliminate the variable x first. To do that, we must make the coefficients of x as additive 

inverse of each other. Since we have a 3 as coefficient of x in the second equation, we will make

the coefficient of x in the first equation as -3.

We multiply both sides of the first equation by -3.

`-3(x - 4y) = -3*0`

`-3x+12y = 0` 

Apply the Addition Method/Elimination Method now.

 `-3x+12y = 0` ``

`+`    `3x - y = 70`

_________________

`11y = 70`  

Isolate the y on left side by dividing both sides by 11.

`y = 70/11`  

Substitute the value of y we got in the first equation.

`4(70/11) = x`  

`x = 280/11`

Therefore, the solution set is (280/11,70/11). 

That is it! :) 

caledon's profile pic

caledon | High School Teacher | (Level 3) Senior Educator

Posted on

This can be solved by substituting the 4y=x value into the second equation.

3x - y = 70

Replace x with 4y;

3(4y) - y = 70

12y - y = 70

11y = 70

y = (70/11) or 6.36

Substituting this into the 4y = x equation;

4(70/11) = x

(280/11) = x or 25.45

You can test this by inserting these values into either equation, or by plotting the equations as a graph and finding the intercept.

Sources:
malkaam's profile pic

malkaam | Student, Undergraduate | (Level 1) Valedictorian

Posted on

4y = x        -------eq(i)

3x - y = 70     ----eq(ii)

The value of x and y can be found through the method of substitution, therefore let us consider eq(i)

x = 4y             ---eq(i)

Input this value of x in eq(ii)

3x - y = 70     ----eq(ii)

3(4y) - y = 70

12y - y = 70

11y = 70

y = 70/11

Now insert this value in eq(i)

4y = x        -------eq(i)

4(70/11) = x

280/11 = x

x = 280/11

Therefore,

x = 280/11 Answer

y = 70/11 Answer.

rachellopez's profile pic

rachellopez | Student, Grade 12 | (Level 1) Valedictorian

Posted on

Because you know the value of x, you can substitute that into the second equation. 

3(4y)-y=70

12y-y=70

11y=70

y=70/11

Now substitute y into the first equation to get x. 

4(70/11)=x

x=280/11

steamgirl's profile pic

steamgirl | Student, College Junior | (Level 1) Honors

Posted on

First, put 3x-y=70 in standard form: y = 3x -70. Now y is equal to two different equations, therefore if these two equations are equal to y, then they must be equal to each other. Therefore, set the 2 equations equal:

x = 3x-70

Solve for x:

2x = 70

x = 35

acompanioninthetardis's profile pic

acompanioninthetardis | Student, Undergraduate | (Level 1) Valedictorian

Posted on

4y=x 3x-y=70

substitute 4y for every x

3(4y)-Y=70

12y-y=70

11y=70

y=70/11

then substitute this for y in the smaller equation

4(70/11)=X

280/11 =x:)

Wiggin42's profile pic

Wiggin42 | Student, Undergraduate | (Level 2) Valedictorian

Posted on

4y=x 3x-y=70

3(4y) - y = 70

12y - y = 70

11y = 70

y = 70/11

x = 4(70/11)

x = 280/11

Jyotsana's profile pic

Jyotsana | Student, Grade 10 | (Level 1) Valedictorian

Posted on

4y=x

3(4y)-y=70

12y-y=70

11y=70

11y/11=70/11

y=70/11

4(70//11)=x

280/11=x

We’ve answered 318,955 questions. We can answer yours, too.

Ask a question