In this case, we'll have to carry out several steps to find the solution.
Step 01:
Data:
expected value of each game = ?
Step 02:
Expected value:
Sister:
total outcomes = 6
1 - 6
probability = 1/6
1 | 2 | 3 | 4 | 5 | 6
$3 | $3 | $3 | $3 | $3 | $3
1/6 | 1/6 | 1/6 | 1/6 | 1/6 | 1/6
expected value (sister) = $3
Mother:
total outcomes = 2
blue - red
probability = 1/2
blue | red
$9 | $21
1/2 | 1/2
expected value (mother) = $15
The answer is:
Expected value (sister) = $3
Expected value (mother) = $15
Mother's offer.