Question

R+12 = 3r + 4
What's the value of r?

Answer 1

r + 12 = 3r + 4
subtract 3r from both sides
-3r + r + 12 = 3r - 3r + 4
-2r + 12 = 4
subtract 12 from both sides
-2r + 12 -12 = 4 - 12
-2r = -8
divide by -2
r = 4

Answer 2

4-12=8 then 3r-r=2r then you're left with 8=2r. 8 divided by two is 4. R=4