Explanation:

- The average score of 8 boys is given as 72. So, the total score by boys is $8\times 72=576$.

- When scores of 3 girls are included, the average increases by 3, making it $72+3=75$ for 11 students.

- Therefore, the total score for 11 students is $11\times 75=825$.

- The total score of the 3 girls is the difference between these two totals: $825-576=249$.

- The average score of the 3 girls is $\frac{249}{3}=83$.

- Option 2: 83 is the correct answer.