Answer:
s = 1/t - 1/r
Step-by-step explanation:
1/r+s=1/t
Subtract 1/r from each side
1/r - 1/r+s=1/t- 1/r
[tex]\huge{\boxed{s=t-r}}[/tex]
if
[tex]\dfrac{1}{r+s}=\dfrac{1}{t}\qquad\text{cross multiply}\\\\(1)(t)=(1)(r+s)\\\\t=r+s\qquad\text{subtract}\ r\ \text{from both sides}\\\\t-r=r-r+s\\\\t-r=s\to\boxed{s=t-r}[/tex]
