math algebra 1
posted by Vamma .
There are 4 times as many nickels as dimes in a coin bag. The coins have a total value of 600 cents ($6.00). Find the number of nickels. Write and solve an equation to do so.
(i found the answer through guess and check but i need to know the equation....btw the answer is 80 nickels and 20 dimes....plz help me find the equation)

Let n be the number of nickels
d the number of dimes
n = 4d because we are told "4 times as many nickels as dimes"
The total value is:
n * 5 + d * 10 = 600
Divide across by 5:
n + 2d = 120
and n=4d, so
4d + 2d = 120
6d = 120
d= 20
So n = 4d = 80