I think I did a) correctly, I'm having trouble understanding and completing b) and c).

In the game of roulette, there is a wheel with spaces marked 0 through 36 and a space marked 00.

a.)Find the probability of winning if you pick the number 7 and it comes up on the wheel.

P(number 7 coming up on the wheel)= 1/38

b.)Find the odds against winning if you pick the number 7.

c.)The casino will pay you $20 for every dollar you bet if your number comes up.How much profit is the casino making on the bet?