Glad you're happy.
Q18
360 = 0.2 a
a = 360 / .2 = 5(360)= 1800 audience members
Q19
Assuming the information is consistent we ignore the trapezoid; we have two triangles base 1.1 height 3.8 so the area for the pair is 2 (1/2) (1.1) (3.8) = 4.18 sq inches.
Q20
6(5)^2 - 5(4) + 8 = 6(25) -20 + 8 = 150 - 20 + 8 = 138
Q21
This is an LCM or least common multiple problem
LCM(12,8) = LCM(3(4),2(4))=3(2)(4)=24 weeks