Answer:
2.5in
Explanation:
Given parameters;
Base = 4.5inches
Height = 6inches
Area = 21in²
Unknown:
b₂ = ?
Solution:
Formula for finding the area of a trapezium;
A =

x h
Input the parameters and solve for b₂;
21 =

x 6
21 = 3(4.5 + b₂)
21 = 13.5 + 3b₂
21 - 13.5 = 3b₂
b₂ = 2.5in