Answer
$t=\frac{2s}{v_1+v_2}$
Work Step by Step
Multiply $2$ to both sides of the equation:
$2(s)=2 \cdot \frac{(v_1+v_2)t}{2}
\\2s= (v_1+v_2)t$
Divide $v_1+v_2$ to both sides of the equation:
$\frac{2s}{v_1+v_2} = \frac{(v_1+v_2)t}{v_1+v_2}
\\\frac{2s}{v_1+v_2}=t$
