Ans: (a) $t=\dfrac{5s}{2}$ (b) $s=274$, $t=685$
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$\begin{array}{rcl}
\dfrac{2s+t}{s+2t} & = & \dfrac{3}{4} \\
4(2s+t) & = & 3(s+2t) \\
8s + 4t & = & 3s + 6t \\
-2t & = & -5 s \\
t & = & \dfrac{5s}{2}
\end{array}$ - Substitute the result of (a) into $s+t = 959$, we have
$\begin{array}{rcl}
s + \dfrac{5s}{2} & = & 959 \\
\dfrac{7s}{2} & = & 959 \\
s & = & 274
\end{array}$Substitute $s=274$ into $s+t=959$, we have
$\begin{array}{rcl}
274 + t & = & 959 \\
t & = & 685
\end{array}$Therefore, $s=274$ and $t=685$.
