Achild bus ticket costs $0.40 and an adult’s ticket costs $0.70. a group of 11 individuals pays $5.90 for their fare. quantity a the number of children quantity b the number of adults which one is bigger? a or b?

Let
A------------> number of children
B------------> number of adults

we know that
0.40A+0.70B=5.90--------------------------> equation 1
A+B=11------------> A=11-B----------------> equation 2

using a graph tool------------> to resolve the equations system
see the attached figure

the solution is 
A=6
B=5

the answer is 
A is bigger