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