Question 116161
0.05n + 0.10d = 6    ----> (1)
0.05(n+6) + 0.10(2d) = 9.90  ----> (2)

equation 2 becomes,

0.05n + 0.20d = 9.60   -----> (3)

solving (1) and (3), we get,

d = 36 and n = 48 where d is the number of dimes and n is the number of nickels.