Hello from MrBillDoesMath!
Answer:
r = 5
Discussion:
2r + 6 + 3r = 31 => (Given)
(2r + 3r) + 6 = 31 => (combine r terms). Subtract 6 from both sides
5r + 6 -6 = 31 - 6 = 25 =>
5r = 25 =>
r = 25/5 = 5
Regards,
MrB