[ Answer ]

[ Explanation ]
- Formula For Area Of Trapezoid:

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A = 10
B = 18
H = 6
- Plug Numbers Into Equation:

10 + 18 = 28
28 ÷ 2 = 14
14 · 6 = 84
84
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Answer:
It takes him 7 minutes to do 21 problems
Step-by-step explanation:
15/5=3
He did 21 problems
So you would then do...
21/3=7
Answer:
3.50+8.74x=y , other answer 47.2