"$8.50"
error: incompatible types: String cannot be converted to int
"$8.50" isn't an int, it is a string, those quotes (opening and closing) denote that. If you'd take quotes off, you'd get also an error about $ symbol.
Think about ints as about whole numbers. And about doubles as about fractional numbers.
Some examples of ints:
0, 1, 2, 100, -100, -1, ...
Some examples of doubles:
0.3, 8.5, 4.2, ...
So you really want not an int, but double maybe for your exercise. Or if you use ints, then convert the price to cents and then pass that amount, i.e. 850 $ cents = $ 8.5