y= quarters Quincy has

5+y= dimes Dirk has

.05(x-1)+.25=.1(5+y-1)+.05

.1(5+y-1)+.05=.25(y-1)+.1

rewrite without decimals by dividing through by .05

x-1+5=2(5+y-1)+1

2(5+y-1)+1=5(y-1)+2

combine like terms and remove parenthesis

x+4=2y+9

2y+9=5y-3→-3y=-12

y=4

x=13

so Natalie has 13 nickels

Dirk has 9 dimes

Quincy has 4 quarters

And after they have swapped coins they all have $.85

D = Q + 5 (make sure and get the sign right)

10(D-1) + 5 = 25(Q-1) + 10 = T (in pennies, where T is the total)

and 5(N-1) + 25 = T

Plug in D = Q+5 in the second equation and solve for Q, this gives (after some work) Q = 4, D = 9, and therefore T = 85. Now you can solve the third equation to get N = 13.

dirk= 5 dimes

quincy= 2quarters

natalie= 9nickels= 45

dirk= 4dimes 1nickel= 45

quincy= 1quarter 1dime= 35.

I dont know..