Question

What is the measure of 21? 100° 90° 80° 85° 95%​

Answer 1

Answer:

A quadrilateral's interior angles have a sum of 360°.

Given that we have 85°, 100°, and 90°(the right angle), and an unknown angle.

We can add these angles plus the unknown angle to equal a total of 360°.

85 + 100 + 90 + x(our unknown missing angle) = 360

simplify

275 + x = 360

Isolate x by subtract 275 from both sides;

-275       -275

x = 85, ∠1 = 85°

We can also double check:-

85 + 100 + 90 + 85 = 360

360 = 360 which is correct.