We breakdown the components of the distances.
(1) 90 miles west.
x - component = -90 miles
y - component = 0 miles
(2) 80 miles, northwest (120°)
x - component = (80 miles)*(sin 30°) = 40 miles (negative)
y - component =(80 miles)*(cos 30°) = 69.282 miles (positive)
Solve for the distance,
√(-90 - - 40)² + (69.282 miles)² = 147.31 miles