10 POINTS.. ILL GIVE BRAINLIEST Solve for x:
a) x = 18
b) x = 19
c) X = 20
d) x = 21

D. x = 21

Step-by-step explanation:

So a straight line is equal to 180º and that's what we're trying to figure out here. Set both equations to equal 180, it should look like:

5x + 4x - 9 = 180

Now we just solve!

5x + 4x - 9 = 180

5x + 4x = 9x

9x - 9 = 180

     +9     +9

9x = 189

Divide both sides by 9 to get x by itself.

189/9 = 21

x = 21

a

step-by-step explanation:

answer: both chords and diameters have two endpoints on a circle. diameters must intersect the center of a circle.