An urn has 5 red, 10 green and 15 yellow marbles. a simple random sample of 5 marbles is taken from this urn. let x denote the number of yellow marbles in the sample. (a) what is the expectation and the standard deviation of x? (b) what is the probability to have exactly 2 yellow marbles in the sample?

the entire expression should be subtracted from 30. to subtract the quantity, distribute the negative sign, which changes the signs on the terms. so, the –2 changes to positive and gets added to 30 instead of subtracted from it.

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step-by-step explanation: