Keystone Algebra I Practice Test 10

Kiran solved an equation as shown below.

Line 1: $x+7=12$

Line 2: $(x+7)+(-7)=12+(-7)$

Line 3: $x+(7+(-7))=5$

Line 4: $x+0=5$

Line 5: $x=5$

Which statement describes the change on the left side from Line 2 to Line 3?