Question

cos 21 degrees = 9/y

Answer 1

Solve for y? :o

Answer 2

\[\Large \cos21^o=\frac{9}{y}\]So if we do a little algebra we can solve for y! :O
Multiplying both sides by y gives us,\[\Large y \cos21^o=9\]We'll isolate the y term by dividing both sides by cos21,\[\Large y=\frac{9}{\cos 21^o}\]

Answer 3

Understand how we did that?
From here we would just want to use our old friend, Mr. Calculator, to get us the final value.