Answer:
(A) 21
Step-by-step explanation:
5x-15 needs to equal 90 since it is a right angle and 21 makes that true
[tex](5*21)=105\\105-15=90[/tex]
A+B=180
(9×+15)×(3×-15)=180
12×=180
×=180\12
×=15 ans,,
