we can use the ratio approach:
if 22% of students equals 165
then how many students equal 100%?
22% = 0.22
100% = 1
the equation would look like this
0.22 = 165
1 = x
now, to solve the equation we multiply values obliquely
0.22 * x = 165 * 1
0.22x = 165 / 0.22
x = 750
there are 750 students in the high school