Question 1065416
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You can make up a table of the 8 possible outcomes and calculate the probabilities of each. 
As you can see the probabilities sum to 1 so all outcomes are covered.
The outcomes that sum to 25 cents are shown in yellow.
These cases are the draws of two dimes and one nickel(NDD, DND, and DDN). 
The probability is calculated as,
{{{P=3(5/9)(4/8)(4/7)=10/21}}}