Question

Prove: if a+c=b+c, then a=b.

Answer 1

Statement 1: a+c=b+c
Statement 2: a+c+(-c)=b+c+(-c)
Statement 3: a+[c+(-c)]=b+[c(-c)]
Statement 4: a+0=b+0
Statement 5: a=b. 
What is the reason for Statement 2? 

A.) Property of opposites

This property is where a number and its opposite are called additive inverses. The sum of these numbers is equal to 0.