Write an equation for each variable.

$\frac{2}{3}\text{A}=\frac{5}{12}$
Now write the second equation for $B$. Solve each equation for
the variable. Compare the value of each.

To eliminate the $\frac{2}{3}$ you don't need to divide using a calculator.
A better strategy is to multiply both sides of the equation by $\frac{3}{2}$, the reciprocal of $\frac{2}{3}$

$B$ is larger.