Answer:
x=15 degrees
Step-by-step explanation:
The given triangle is isosceles, so both base angles are both (3x+18).
We also know that angles on a line add up to 180 degrees, so
(3x+18) + (8x-3) = 180 degrees
Simplify
11x + 15 = 180 degrees
11x = 180-15 = 165
Divide by coefficient on left-hand side
x = 165/11 = 15 degrees.
