Answer:
5
Explanation:
sum the parts of the ratio, 3 + 4 = 7 parts
Divide the number of students by 7 to find the value of one part of the ratio
35 ÷ 7 = 5 ← value of 1 part of the ratio, then
3 parts 3 × 5 = 15 ← number of boys
4 parts = 4 × 5 = 20 ← number of girls
20 - 15 = 5
There are 5 more girls than boys