Let's find the value of x
Since the sum of internal angles of a triangle is 180°
therefore,






I could be wrong but this is what I think.
D=RT
D=39 (3)
D=117
I'm thinking that its 4 because.....
you add 5x on each side, u put the 5 in the parenthesis and replace the x with 5 then you'll end up having f(5)=4. How's that?