Solve the equation for the specified variable.?

Question

The simple interest formula: P = A / 1+rt ; for r

Answer 1

P = A / (1+rt )
Switch P and 1+rt,
1+rt = A/P
Solve for r,
r = (A/P - 1)/t = (A-P)/(Pt)

Answer 2

A/P= 1+rt so r=(A/P -1)/t