This is a question on finding the Highest Common Factor (HCF) of a given set of numbers.
Since we have to minimize the number of notes that the teller has to vend out, we have to make sure that we divide each of the sums by the largest possible number that can divide all of them. Clearly, this has to be their HCF. Now, to calculate their HCF.
750 = 2 * 3 * \(5^3\)
500 = \(2^2\) * \(5^3\)
600 = \(2^3\) * 3 * \(5^2\)
HCF = 2 * \(5^2\) = 50.
Therefore, $750 can be dealt out with 15 notes of $50. $500 as 10 notes of $50 and $600 as 12 notes of $50. The total number of notes dealt is (15 + 12 + 10) i.e. 37.
So, the correct answer option is D.
Clearly, the last part of the question statement (which was missed out when I first posted the question) is a clear clue that the sums 750, 500 and 600 have to be divided by a common value. The first part of the question statement tells us that we need to divide it by the highest such common value because we are trying to minimize the number of notes. This should tell you that the HCF of these numbers has to be the intermediate answer that will eventually help you calculate the final answer.
Had 50 been one of the options, things could have been more interesting

. Hindsight is always beneficial
Hope this helps!