Explanation

(d)
According to question,
$w_{A} = \ xg,\$ $m_{A} = \ 18,$ $x_{A} = \ 1 - 0.6 = 0.4\$
$w_{B} = 69g,\ \$ $m_{B} = \ 46,\$ $X_{B} = \ 0.4\$
We know that,
$X_{A} = \frac{n_{A}}{n_{A} + n_{B}}$
or 0.4= $\frac{w_{A}/m_{A}}{\frac{w_{A}}{m_{A}} + \frac{69}{46}}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 0.4 = \frac{x/18}{\frac{x}{18} + \frac{3}{2}}$
0.4$\times \ \left( \frac{2x + 54}{36} \right) = \frac{x}{18}$
or 2x+54=5x
or 3x=54,x=18 g