Question

What should be added to both sides of this equation to solve for the variable? r + (-12) = 19

Answer 1

12

So,
r+ -12+ 12 = 19+ 12
r+ 0 = 31
R=31

Answer 2

12

Explanation:

Then the -12 and +12 will cancel out, so you're left with a clean isolated r on the left:

r -12 +12 = 19 + 12

r = 31