How would I solve this trig equation?

sec(90-x) = 1/cos(90-x) = 1/sin(x) = 3
so 3*sin(x) = 1
so sin(x) = 1/3
so x = arcsin(1/3) = asin(1/3) = 19.471220634491 ~ 19.47 degrees

(90-x)=3
1) Put all the variables in the left side and the constants, in right side. Remember: Be careful with the signs; (ex: -x=3-90)
2)Subtract 90 to 3. (ex: 3-90= -87; so -x= -87)
3) Divide -x and -87 by -1.
-x = -87
---- -----
-1 -1
So X =87