F(x) = sqrt(4-x)
You can get this by switching f(x) and x and then solving for f(x).
#include
int main()
{
int num;
scanf("%d", &num);
printf("%d", num*num);
return 0;
}
I need some love in my life
You get everything you need from factoring the last expression:

The left side is a difference of squares, and we get another difference of squares upon factoring. We end up with

Plug in everything you know and solve for
:

Do a proportion
65/100= x/80
Cross multiply and divide
80 x 65= 5, 200
5, 200 divided by 100 is 52
52 members left
80-52= 28
Answer is 28 members