Pls me on this question

15. the shaded region represents the space used for a pool in ms. perez's (1 point)
backyard. her backyard is 10 units long and 10 units wide.

[picture attached]

what is the area of the space that is not used for the pool?
16 square units
40 square units
64 square units
84 square units

second option

step-by-step explanation:

the measures of a triangle equal 180. use that to find x.

2x+3x+4x=180

9x=180

9x/9=180/9

x=20

now you know x, you know angle a is 40°, angle b is 60°, angle c is 80°.

because angle a is 40°, the first option doesn't work.

because angle b is 60°, the second option does work.

when you add angle a and b, you get 100°. complementary means it equals 90°, so the third option doesn't work.

when you add angle a and c, you get 120°, which is not 100.