A proportion looks like this:

It means that the quantity a,b,c and d are in the same proportion: the ratio between a and b is the same ratio between c and d.
They are particularly useful in situation when you have an example given, and you want to extrapolate the relationship for another couple.
For example, you can think of the following problem: "Five apples cost 2 dollars. How much will 8 apples cost?"
You can build the proportion

And then solve it for x:

Area of the sector = 1/2 * r^2 * theta where theta is the angle subtended by the arc at the center ( in radians)
In this case m < theta = 360 - 235 = 125 degrees or 2.182 radians
So, the area of shaded area = 1/2 * 20^2 * 2.182 = 436.4 in^2
Answer:
-25
Step-by-step explanation:
g(f(3))= g(-5)
=4(-5)-5
= -20-5
=-25
10x^2 = 50x.....subtract 50x from both sides
10x^2 - 50x = 0...factor
10x(x - 5) = 0
10x = 0
x = 0 <== this one is eliminated because x cannot be zero
x - 5 = 0
x = 5 <== ur answer