tehhe

let:
x = number of $2 coins
y = number of 50c coins

total number of coins is 17:
x + y = 17....(1)
y = 17 - x ...(1*)

total value is $22:
2x + 0.5y = 22....(2)

Sub (1*) into (2)
2x + 0.5(17 - x) = 22
2x + 8.5 - 0.5x = 22
2x - 0.5x = 22 - 8.5
1.5x = 13.5
x = 9

Sub x into (1*)
y = 17 - 9
y = 8


THEREFORE:
There are 9 $2 coins and 8 50c coins