Explanation
54 people of the 180 surveyed prefer a sports drink.
That's 54/180 = 0.30 = 30% of the sample.
If the sample is representative of the population, then we should expect around 30% of the population prefers a sports drink.
30% of 2000 = 0.30*2000 = 600 people in the entire school are estimated to name sports drink as their favorite.
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Another way to solve
54/180 = x/2000
54*2000 = 180x
x = 54*2000/180
x = 600