SOLUTION: Problem: 5x - 4y + z when x = 6, y = -5 and z = 3 Answer: 53 The way I wrote it is: 5(6) - 4(-5) + 3 30 - (-20) + 3 = 13 Question: Why did the minus turn to posit

Question 401566: Problem:
5x - 4y + z when x = 6, y = -5 and z = 3
Answer:
53
The way I wrote it is:
5(6) - 4(-5) + 3
30 - (-20) + 3
= 13
Question:
Why did the minus turn to positive and the negative 20 turn positive 20?
Is there a time that this does not occur?
Please, keep this simple. I am already having a difficult time.
Answer by richard1234(7193) (Show Source): You can put this solution on YOUR website!
Two negative signs essentially cancel out, leaving a positive. Here's why:

The negative of a number, x, is a number that satisfies "x plus the negative of x equals zero." Therefore the negative of x is -x. The negative of -x is the number such that, when added to -x, produces 0. Here, x is the number that satisfies, since (-x) + x = 0, so -(-x) = x.
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