Answer:
Hello,
Total number : 70
Step-by-step explanation:
20 + 25 = 45
45 liked music
X liked sport only
X + 25 liked sport
45 / 9 = (X + 25) / 7 ⇔ 7 x 5 = X + 25 ⇔ X = 35 - 25 ⇔ X = 10
10 liked sport only
Total students in group : 45 + 10 + 15 = 70