Hello!
To find the base of a trapezoid you use this equation
[tex] \frac{a+b}{2} h[/tex]
Where "a" is base 1, "b" is base 2 and "h" is height
Then you input the numbers
[tex] \frac{18+22}{2} *8.5[/tex]
22 + 18 is 40
40 divided by 2 is 20
and 20 times 8.5 is 170 which is the answer
Hope this helps!
