Question 800980
let q, n and d be number of each coin, worth 25c, 5c and 10c
25q+5n+10d=375
q=n-1
2n=d

substitute for d and q
25n-25+5n+20n = 375
50n=400 so n=8
then d=16 and q=7
8 nickels, 16 dimes and 7 quarters

Check: 25*7 + 5*8 + 10*16 = 175+40+160 = 375