You can
put this solution on YOUR website!80 people are there so first equation is
a+c=80....(1)
second equ formed by condition is
c=4a ....(2) subtacting both equations
a=80-4a
a+4a=80
5a=80
a=80/5
a=16 so c=4(16)=64 there were 64 children in the group