How to calculate ten percent of something?

What is the equation of the graph below? y=sec(x)-4

Select the correct answer from the drop-down menu. subtracting 3xy^2 from 8xy^2 gives the same result as the expression. [tex]3xy ^{2} - 8xy ^{2} [/tex][tex] { - 7xy}^{2} - {2xy}^{2} [/tex][tex] {7xy}^{2} - {2xy}^{2} [/tex]

Iwill give ! if m∠a=59 and m∠3=81°, what is m∠b? m∠b= _[blank]_°