When all sides of a quadrilateral are equal (indicated by tick marks on the four sides) in length and connect the opposing vertices with a line, it will form four 90° angles. Therefore, each equation will equal 90.
10x= 90
x+y= 90
3z= 90
The measure of angles 1 and 3 can be solved as they are so:
10x= 90 ➡️ x=9
3z= 90 ➡️ z= 30
The value of x is needed to solve for the measure of angle 2 so plug in the value of x and solve:
x+y= 90
9+y= 90
y= 81
Therefore the answer is a.
