Question

what is the value of b?

Explanation:

Step1: Recall angle - sum property

The two angles are adjacent and form a right - angle (assuming the vertical and the slanted line form a right - angle situation). The sum of adjacent angles that form a right - angle is 90°.
Let the given angle be 40° and the unknown angle be \(b\). Then \(b + 40^{\circ}=90^{\circ}\).

Step2: Solve for \(b\)

Subtract 40° from both sides of the equation \(b+40^{\circ}=90^{\circ}\). So \(b = 90^{\circ}-40^{\circ}\).

Answer:

50