Answer:
b1 = 9 cm
Step-by-step explanation:
The formula for area of a trapezoid is
A = 1/2 (b1+b2) *h
We know Area = 135 CM ^2, Height = 10 CM, b2 = 18 cm
Substituting these in
135 = 1/2 (b1+18) *10
Multiply 1/2*10
135 = 5 (b1+18)
Divide both side by 5
135/5 = 5/5 (b1+18)
27 = b1+18
Subtract 18 from each side
27-18 = b1+18-18
9 = b1
