Hey!
Hope this helps...
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When looking at this graph we see 2 things:
(1) How they made the graph, looks awful, anyway...
(2) They practically give you the answer...
When finding an answer to a question like this, you want to use a formula (like this):
A = t * p (where A is the amount of people, t is total amount of people, and p is percent of people / 100)...
So... we fill in the givens...
We know t = 400, and (by looking at the graph) we see that p is around 0.10 and 0.15. So for our sake we'll make p = 0.13 (about halfway)...
A = 400 * 0.13
A ~ 52
The answer is: About 52 people bought 20 items...
And because we got 52, and 52 is close to 54...
The Answer: B.) 54