Hello from MrBillDoesMath!
Answer:
x = 21.93 (approx)
Discussion:
The two small triangles are congruent by ASA (each contains a right angle and equal base angles as the large triangle is isosceles). Applying Pythagoras gives
20^2 + (18/2)^2 = x^2 = > as 20^2 = 400 and 9^2 = 81
400 + 81 = x^2 =>
x^2 = 481 => take the square rot of both sides
x = 21.93 (approx)
Thank you,
MrB
