Answer: 9 months
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Explanation:
She read 40 books over 5 months. This means her unit rate is 8 books per month (since 40/5 = 8)
x = number of months
(unit rate)*(number of months) = total books read
8x = 72
x = 72/8
x = 9
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Another way to solve
(40 books)/(5 months) = (72 books)/(x months)
40/5 = 72/x
40x = 5*72 ... cross multiplying
40x = 360
x = 360/40
x = 9
