-5 - (+7) = ?  Can you give us the answer and explain why please.  Thank you.

Expert Answers

An illustration of the letter 'A' in a speech bubbles

There can be lots of ways to describe this.  I like using money.  For instance, a negative number means you "don't have" that much money, or you "owe" that much money.  Subtraction would mean you "owe even more money" or "someone took even more money".  So, if you start out with "owing 5 dollars".  Then, you find out that one of your kids took 7 more dollars out of your wallet ("took out", "took away", subtraction), then you would be in the hole 12 dollars, or -12.  So, the answer would be -12.

Approved by eNotes Editorial Team
An illustration of the letter 'A' in a speech bubbles

- 5 - (+7) = - 5 -7 = -12

When the terms are taken out of the bracket the signs multiply with each other, and the product of a negative and a positive sign is always negative, 

i.e. -1 x + 1 = -1

in our case, we can also write the given equation as

- 5 + (-1)x(+1)x (7) = -5 +(-1)x(7) = -5 -7 = -12.

Hence proved. 

Approved by eNotes Editorial Team