Question 959163
x = number of 25 cent coins
y = number of 3 peso coins


x + y = 20
25x + 300y = 875


300x + 300y = 6000
-25x - 300y = -875
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275x = 5125
x = 18.63...


You can't have a fractional amount of a coin, so this problem has no solution.