Problem solving and Using formulas

Question

Solve the following formula for the specified variable.

A = 1⁄4 m(r+k) for r

Answer 1

Pure algebra:

1) multiply both sides by 4 -> 4A = m(r+k)

2) use the distributive property -> 4A = mr + mk

3) isolate the r term -> 4A - mk = mr

4) divide both sides by m -> 4A/m - k = r