Question 745806
x is number of nickels
y is number of dimes

5x + 10y = 115  

x + y = 20 as there are 20 coins total. 

10x + 10y = 200  (multiplie last equation, both sides by 10)
5x  + 10y = 115  (first equation)

5x = 85   (subtracted second equation from first here )
x = 17  (85 cents)
y = 3   (30 cents)