Answer
x=33
Explanation:
since they're both on the same line we must equal them to 180.
18 + x + 4x -3 = 180 (Now you simplify terms)
5x + 15 = 180 (Subtract the 15 from both sides)
5x = 165 (divide by 5 to isolate the variable)
x = 33 (Hope I was able to help :) )