The equation given to solve is 2x + y = 6.

This equation has two variables x and y. To find a unique value for 'n' variables the number of equations available should be also be n.

Else we can only treat any one of the variables as a constant and express the value of the others in terms of that variable. Also, as the variable we are taking as a constant is not actually a constant, it can change and there are an infinite number of solutions for all the variables. They would only be related to each other in some way by the system of equations.

Here 2x + y = 6,

Subtract 2x from both sides of the equation:

=> y = 6 - 2x

For any value of x there would be a unique value for y. Both the variables can take on an infinite number of values. They would only have to be related with y = 6 - 2x.

2x + y = 60

If you are solving for y your mission is to get y alone by this i mean make

2x + y = 60 into y = whatever the answer is

In order to do this you need to add the opposite of whatever number you are trying to get rid of in this case 2x so we add -2x to get rid of it:

2x - 2x + y = 60 - 2x

simplify:

y = 60 - 2x

You can never have two unknown variables ( x and y). Therefore you need to find a variable first. the easiest way to do it is set a variable equal to zero...

2x+y=60

x=0

2(0)+y=60

y= 60

then use the same equation which you gave (2x+y=60) but since you just found that y=60 use 60 instead of y