Kevin and randy muise have a jar containing 68 coins, all of which are either quarters or nickels. the total value of the coins in the jar is $13.40. how many of each type of coin do they have?

For this case, the first thing we must do is define variables:
 x: number of quarters
 y: number of nickels
 We now write the system of equations:
 x + y = 68
 0.25x + 0.05y = 13.40
 Solving the system we have:
 x = 50
 y = 18
 
 they have:
 quarters = 50
 nickels = 18