Question

im pretty sure when you change the sign in an equation you actually have to change all of them so the equation would be 3+5+7. Am i correct?

Answer 1

1

Explanation:

Mistake in the second step.

We must add positive numbers or negative ones.

Here he had add the positive and negative numbers and that is the mistake

`=3-(-5)-7\\\\=3+5-7`Here 5 is positive because -×-=+

`=8-7`

`=1`

In the second step, we must add the positives that are 3 and 5 and subtract from 7.

Hope it will help you.