It looks like the ∩ sign may be missing from the question. If you mean to find A∩C, called the intersection, you're looking for elements that are both in A and C.
{0, 2} qualifies.
The first one is 84 ounces and the second one is 20 ounces
If half of two acres was planted with green beans, the answer would be one acre
Observe attached picture.
On picture we have:
A = height of flagpole = x ft
B = length of flagpole's shadow = 24 ft
C = height of sign = 6 ft
D = length of sign's shadow = 3 ft
When we draw a picture representing this problem we can also add another line marked in red. This way we can see that we have two right-angle triangles. We can see that both have same angle marked with α.
We can apply trigonometry rules to find height of flagpole.
From small triangle containing sign we can find tangens function:

Similarly we can do for large triangle containing flagpole:

We see that these two equations have same left sides. This means that their right sides must also be same:

We can solve for A:

Height of flagpole is 48 feet.
Set up a proportion. 2/5 = x/40
to solve the equation first cross multiply.
x*5=40*2
x*5=80
now divide both sides by 5, 80 divided by 5 is equal to 16.
so the number of girls in the computer lab is 16.