4th grade math
posted by Dan .
R^2 + R^2 + 16R + 64 = 144
solve for R.

Gee, I didn't learn any algebra until the ninth grade. What you have can be reduced to something called the quadratic equation.
2R^2 + 16R 80 = 0
R^2 +8R 40 = 0
R = (1/2)[8 +/sqrt224]
= 3.4833 or 11.4833
There are no integer solutions.
Are you sure you didn't mean to write
R^2 + 16R + 64 = 144 ?
That has a simpler solution that you can get by taking the square root of each side.
(R + 8)^2 = 12^2
R = 8 +or 12 = 20 or +4