Sydney has 24 coins that are a mixture of nickels and dimes that are worth $1.95. How many dimes does she have?

 15  dimes

Step-by-step explanation:

Nickels are 5 cents and dimes are 10 cents  and since they are a total of 1.95 coins in total we can set up the two equations and solve for how much there are for each of the money.

x + y = 24  

0.05x + 0.10y = 1.95   so solve for  y  and  x is the number of nickels while y is the number of dimes.

x+y=24

   -y    -y

x = -1y +24  

0.05(-1y +24) + 0.10y = 1.95

 -0.05y + 1.2 + 0.10y = 1.95

       0.05y + 1.2 = 1.95

                     -1.2   -1.2

          0.05y = 0.75

   y = 15

60%