Answer
The height of the main sail is $13$ ft.
Work Step by Step
We can use the law of sines to relate the two angles and their opposite sides to one another:
$\frac{sin 42^{\circ}}{12} = \frac{sin 48^{\circ}}{h}$
Multiply each side by $h$:
$\frac{sin 42^{\circ}}{12}(h)$ = sin $48^{\circ}$
Divide each side of the equation by $\frac{sin 42^{\circ}}{12}$ to solve for $x$:
$h \approx 13$ ft.
The height of the main sail is $13$ ft.
