Hey there! This situation can be modeled and solved using a system of equations. We'll use 
to represent the number of boys and 
to represent the number of girls.
Since we know what equals, we can substitute it into the first equation.
Now that we know the number of girls, use the second equation to get the number of boys.
Try this:
21/7=3
multiply 3x2
x=6
y=21 x=6
or...
7/2=21/x
cross multiply to get 7x=42
divide by 7 and x=6
Answer: he paid for 5 hours take
51.00-11.00 = 40.00 left
8/40= 5
so he paid for 5 hours
Answer:
3.14 or pi
Step-by-step explanation:
the area of a circle = 
where r is the radius of the circle
this is 1/4 of the circle, so it would be 1/4 (pi * r²)
it shows that the radius is 2, so you have
1/4 ( pi * 2²)
= 1/4 ( pi * 4 )
= 1/4 (3.14 * 4)
= 3.14 units²
