A radio station gives away $15 to every 15th caller, $25 to every 25th caller, and free concert tickets to every 100th caller. When will the station first give away all three prizes to one caller? PLEASE HELP. Show your work !!

The answer is 300th caller.
to find the answer you have to take the LCM of all three numbers of callers that are 15,25 and 100
so, lets take the LCM
5     15, 25, 100
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5      3, 5, 20
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3      3, 1, 4
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4       1, 1, 4
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          1, 1, 1
Now ,multiply the numbers 5,5, 3 and 4.
5 x 5 x 3 x 4 = 25 x 12 = 300