7) B

Since no boys chose rounders, all children who chose rounders must be girls.

Number of girls that chose rounders = 10 + 6 + 14 + 10 = 40

Number of children that chose running = 10 + 6 + 6 + 6 = 28

Since equal number of boys and girls chose running, number of girls that chose running = 14

Number of boys that chose running = 14

Since no girls chose swimming, all children who chose swimming must be boys.

Number of boys that chose swimming = 4 + 6 + 8 + 10 = 28

Let total number of boys = B

Let total number of girls = G

Equal number of boys and girls took part in the survey.

B = G

Let total number of boys that chose football = P

Let total number of girls that chose football = Q

B = G

14 + 28 + P = 14 + 40 + Q

P = Q + 12

Total number of children that chose football = 11 + 11 + 14 + 12 = 48

We know that P + Q = 48

Since P = Q + 12

Q + 12 + Q = 48

2Q = 36

Q = 18