Answer:
The outcome of rolling a set of 2 fair dice is a number between 2 and 12, and there is a probability of 1/9 for each outcome.
For the outcomes 4,5,6, you will lose $6, and for the other outcomes, you will win $3.
There are 3 outcomes 4,5,6, and 9-3 = 6 outcomes where you win $3.
So your expected gain/loss per roll is:
(3/9) * $3 + (3/9) * (-$6) = -$1
Therefore, on average, you will lose $1 per each throwing.