Question 15395
Let x = number of nickels
4x = number of dimes


Number of pennies = (total number of coins) - (sum of the nickels and dimes)
80 - (x+4x) = number of pennies
80-5x = number of pennies


Total value = value of each type of coin times the number of coins.
Value = 5(x) + 10(4x) + 1(80-5x)
Value = 5x + 40x + 80 - 5x 
Value = 40x + 80


That's it!  Of course you can't solve it since you don't know the total value of all the coins.


R^2 at SCC