Can someone please explain: (+8) + (-15) { = -(15-8) , Correct Answer is -7 } My answer is +7, which is wrong. Need clarification.

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justaguide's profile pic

justaguide | College Teacher | (Level 2) Distinguished Educator

Posted on

You have (+8) + (-15) = -(15 - 8)

The result of this is -7 because you simplify the expression as follows:

(+8) + (-15)

remove the brackets, as the sign before (-15) is +, eliminate it without altering -15.

=> 8 - 15

=> -7

[ If there is a minus sign before the brackets, when the brackets are opened the sign of all the terms in the brackets are reversed, else for a plus sign before the brackets they remain the same. ]

Here the terms 8 and -15 are being added, the result will be a negative number given that 15 > 8 and equal to 7 as 15 - 8 = 7.

Hope the explanation helped.

The result of (+8) + (-15) = -7

academicsfirst's profile pic

academicsfirst | High School Teacher | (Level 2) Adjunct Educator

Posted on

We will verify that the correct answer to (8) + (-15) = -(15-8) is -7.

=>  (8) + (-15) = -(7)

=>  8 - 15 = -7

=>  -7 = - 7

(8) + (-15) = -(15 -8)  has been verified.

The correct simplification is -7.

giorgiana1976's profile pic

giorgiana1976 | College Teacher | (Level 3) Valedictorian

Posted on

We'll start from the fact that adding a negative number to another number is the same thing as subtracting a positive number.

In this case, to add the negative number -15 to the number +8 is same as subtracting 8 from 15.

Now, the result will have the symbol of the larger number, which in this case is 15.

8 - 15 = -7

To the right side of the equl sign, you'll find the mathematical explanation of the facts described above.

8 - 15 = -(15 - 8) = -7

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