Answer: Barlow has more by 178
Explanation:
Solve for Barlow first: 4/9 of 873 is 388 boys.
Solve for Willow: since 2/3 of the students are girls, that means that 1/3 of them are boys: 1/3 of 630 = 210
Barlow has more, now find out by how many: 388 - 210 = 178.