Question 41088
Let n be the number of nickels, and then d will be the number of dimes.  Their values will then be 5n and 10d respectively...then we have
5n + 10d = 330 (thinking in cents now)
n + d = 42
If we multiply the bottom one by 5 and subtract, 
5n + 10d = 330
-(5n + 5d = 210)
we get
5d = 120
d = 24 and
n = 18
Check to see they add to $3.30...