Explanation:
I assume you meant :
the restaurant has 20 1/2 pounds of bananas.
one smoothie uses 1/8 pound of bananas.
how many smoothies can be made with the amount of available bananas ?
the answer is as many as the times 1/8 fit into 20 1/2.
so, we actually calculate
(20 1/2) / (1/8)
first we will convert the mixed number into a true fraction :
20 1/2 = 40/2 + 1/2 = 41/2
so we have
41/2 / 1/8
and then, when dividing fractions we have 2 choices (they do both the same, of course, but start looking differently) :
a/b / c/d = a×d / b×c
a/b / c/d = a/b × d/c = a×d / b×c
so,
41/2 / 1/8 = 41×8 / 2×1 = 41×4 = 164
they can make 164 smoothies.