Answer
$sinB=0.678$
Possible values of B are $B_{1}=42.7^{\circ}$ & $B_{2}=137.3^{\circ}$
Work Step by Step
$A=40^{\circ},b=19ft,a=18ft$
Using laws of sines,
$\frac{sinA}{a}=\frac{sinB}{b}$
$\frac{sin40^{\circ}}{18}=\frac{sinB}{19}$
so,$sinB=0.678$
There are 2 possible values of B,
so $B_{1}=42.7^{\circ}$ & $B_{2}=180^{\circ}-42.7^{\circ}=137.3^{\circ}$
so $B_{1}=42.7^{\circ}$ & $B_{2}=137.3^{\circ}$
