Answer:
[tex]s=\frac{u}{r} -\frac{t}{r}[/tex]
Step-by-step explanation:
You have to move the variables (r and t) with u to isolate s.
[tex]rs+t=u[/tex]
[tex]-t[/tex] [tex]-t[/tex]
------------------------
[tex]rs=u-t[/tex]
÷ [tex]r[/tex] ÷ [tex]r[/tex]
------------------------
[tex]s=\frac{u}{r} -\frac{t}{r}[/tex]
