Answer
$β = 40˚$
Work Step by Step
Let $x =$ the one of the unknown angle
$\frac{sin(x)}{7} = \frac{sin(70)}{7}$
$sin(x) = sin(70)$
$x = sin^{-1}(sin(70))$
$x = sin^{-1} (sin(0.9396))$
by Graphic Display Calculator / GDC
$x = 70˚$
2. Add the first 2 known angles and subtract from $180˚$ to solve for $β$
$β + 70 + 70 = 180$
$β + 140 = 180$
$β = 40˚$
Therefore, $β = 40˚$.
