Answer: 21.3
Step-by-step explanation: Let us split the figure into two triangles. If the total bottom length is 22, than the triangle's base is 22/2=11
We can use the Pythagorean theorem to get: 11^2+x^2=24^2 or 121+x^2=576
576-121=455
sqrt 455=21.33................
rounds to 21.3