Question 479070
let x=  random variable for the earnings

If only one ticket is bought, 
If x = -5, then p(x) = 99/100, 
If x = 495, then p(x) = 1/100, and so
E(x) = -5*(99/100) + 495*(1/100) = 0, the expected earning.

If 2 tickets are bought, 
E(X) = -10*(98/100) + 490*(2/100) = 0, the expected earning.

Both games are fair.