3a) Answer: 84 degrees
Step-by-step explanation:
3x + 2(x+20)= 180 (total sum of angles in a triangle is 180 degrees)
5x+40 = 180
5x = 140
x= 28
3x= 28 x 3
= 84
So, when we're tasked with things like this, rewriting everything in terms of sine and cosine and combining fractions often trivializes things, so doing just that gives us:

So out expression is 1/cos(x).
-4 - 1 = -5 can be an equation that equals -5.