Question

Rx-st=r solve equation for s

Answer 1

Rx - st = r

Rx = r + st                                       Add st to both sides

Rx - r = st                                        Subtract r from both sides

(Rx - r)/t = s                                     Divide t on both sides ( to isolate s)

Answer 2

$rx-st=r\qquad\text{subtract rx from both sides}\\\\-st=-rx+r\qquad\text{change the signs}\\\\st=rx-r\qquad\text{divide both sides by}\ t\neq0\\\\\boxed{s=\dfrac{rx-r}{t}}$