susan has a collection of 40 nickels and dimes. if the number of nickels is three times the number of dimes, how many nickels and how many dimes does she have?

Question

i don't know what to do

Answer 1

Let N be the number of nickels

Let D be the number of dimes

 

N + D = 40           eq. 1

 

N = 3D                  eq. 2

 

substitute eq.2 to eq. 1

 

3D + D = 40

 

4D = 40

 

D = 10

 

so, N = 30.

 

10 dimes and 30 nickels