Answer:
$346.50.
Step-by-step explanation:
Imagine that the 9*9 square on the left is a part of the floor then:
The area = area of a trapezium - 9^2.
So the area of the dining area = 1/2 * (31 + 21) * 12 - 9^2
= 231 ft^2.
So they should plan to spend 231 * 1.5 = $346.50.
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