Pr(3 heads) + Pr(3 tails) = (1/2)^3 + (1/2)^3 = 1/4.

Let X be the random variableamount of money won by you in a game.

E(X) = (1/4)(4) + (3/4)(-1.5) = ......

If the game is fair, E(X) = 0.

If E(X) < 0, the game is unfair to you (why?)

If E(X) > 0, the game is unfair to your friend (why?).