Answer:
300
Explanation:
Sum the parts of the ratio, 3 + 4 = 7 parts
Divide the total by 7 to find the value of one part of the ratio.
700 ÷ 7 = 100 ← value of 1 part of the ratio, thus
3 parts = 3 × 100 = 300 ← number of girls
4 parts = 4 × 100 = 400 ← number of boys