2018-I-01

Ans: $b = \dfrac{2a+5}{3}$
$\begin{array}{rcl}
\dfrac{a+4}{3} & = & \dfrac{b+1}{2} \\
2(a+4) & = & 3(b+1) \\
2a + 8 & = & 3b + 3 \\
2a + 5 & = & 3b \\
3b & = & 2a + 5 \\
b & = & \dfrac{2a + 5}{3}
\end{array}$