Question

7. Determine the measures of the two angles that are not 90° in the diagram below. Show your

Answer 1

First we need to assume that the sum of the angles is also 180°. if one is less than 90°, the other will be more. we can do this because in a plane 4-sided polygon the sum of the inner angles will always be 360°, and we already know the two angles on the right side

so we can say that:

3x + 20 + x = 180

Since we got only one variable in this equation, we can already solve for x.

4x + 20 = 180

4x = 160

x = 40

the lower left angle is just 40°

the upper left is three times that plus 20, so it's 160°

hope this helps you to get the method