Question

3-(-5)-7
= 3 + 5 - 7
Step 1
= 3 + 2
Step 2
= 5
Step 3
Find Paolo's mistake.

Answer 1

When Paolo tried to simplify 5 - 7 at Step 2, instead of keeping the sign of the answer, -2, he added it. He really should have written 3 - 2.

Answer 2

Paolo should have multiplied 3 times positive 5 rather than adding it. The parenthesis means multiplication. :)