Please explain how to do this Will give Brainly

Answer
11 children tickets were sold and 10 adult tickets were sold.
Step-by-step explanation:
Okay first set your variables
x=adults 6x
y= children 4y
the first equation will be 6x+4y=104
the second will be x+y=21 because she sold 21 tickets
now this is a substitution equation. so, we rearrange the second equation so y=-x+21
now substitute the y in the first equation
6x+4(-x+21)=104
distribute the properties and you get
6x-4x+84=104
2x+84=104
move your 84 and change the sign
2x=20
x=10
now you put x into the first equation,
6(10)+4y=104
60+4y=104
move your 60 and change the sign
4y=44
y=11
So 11 children tickets were sold and 10 adult tickets were sold.