The labeled angle is what's called an inscribed angle. There's a theorem (fittingly called the inscribed angle theorem) that says the measure of this angle is half the measure of the circular arc that it subtends.
In this case, the angle is subtended by an arc measuring 180°. So
(4x + 6)° = 1/2 • 180°
4x + 6 = 90
4x = 84
x = 21
The way to get the equation for the radius (r) is to get r by itself. So divide each side by 4pi
500/4pi=r^2
Now take the square root of each side to get the equation of r.
sqrt(500/4pi)=r
Set up a proportion: 25/100 = 50/n where n = # of teens surveyed
Simplify fraction: 1/4 = 50/n
Cross multiply: n = 200
So 200 teens were surveyed.
it’s basically just any number that can be multiplied with another to get a new expression
