Question

each row contains the measures of 2 angles for a triangle. for each triangle, select the measure of the third angle. answers may be used more than once. 30° 40° 50° 80° and 100° 55° and 75° 60° and 90° 65° and 75°

Explanation:

Step1: Recall angle - sum property

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

Step2: Calculate for 80° and 100°

Let the third angle be $x$. Then $x=180-(80 + 100)=0$ (This is an error in the problem - setup as a triangle can't have an angle of 0°, but following the formula).

Step3: Calculate for 55° and 75°

Let the third angle be $y$. Then $y = 180-(55 + 75)=180 - 130 = 50^{\circ}$.

Step4: Calculate for 60° and 90°

Let the third angle be $z$. Then $z=180-(60 + 90)=180 - 150 = 30^{\circ}$.

Step5: Calculate for 45° and 75°

Let the third angle be $w$. Then $w=180-(45 + 75)=180 - 120 = 60^{\circ}$ (but 60° is not in the options, and if we assume a correct - format problem, following the formula).

Answer:

For the pair 55° and 75°, the third - angle is 50°.
For the pair 60° and 90°, the third - angle is 30°.