Question

a = 60
blank 1: 60

Explanation:

Step1: Recall angle - sum property

The sum of interior angles of a triangle is 180°.

Step2: Set up equation

Let the unknown angle be $\alpha$. We have $\alpha+70^{\circ}+50^{\circ}=180^{\circ}$.

Step3: Solve for $\alpha$

$\alpha = 180^{\circ}-(70^{\circ}+50^{\circ})=180^{\circ}-120^{\circ}=60^{\circ}$.

Answer:

60