Answer: 3
Step-by-step explanation: let first consider a single spin.
Number of possible outcomes = 7
Number of required outcome = 4
Probability = 4/7
For the 7 times will be = 4/7 × 7 = 4
Standard deviation = root(4/7 × 3/7)
Standard deviation = 0.495
Standard error = root(7) × 0.495 = 1.3
The expected value = 4 - 1.3 = 2.7
Therefore, the expected value is approximately = 3