Question

You have to get the R by itself

Answer 1

If A = r / 2L, multiply both sides by 2L.

2L cancels itself out and the new equation is (A)(2L) = r.

Answer 2

A = r/2L

A(2L) = r/2L(2L) (multiply 2L to both sides to isolate r)

A(2L) = r is your answer

hope this helps