How many ways can a president and vice-president be selected in a class of eighteen students?

306

Step-by-step explanation:

There are 18 ways to pick the president

Now there are only 17 students left

there are 17 ways to pick the vice president

18 * 17 =306

There are 306 different ways to pick a president and vice president

step-by-step explanation:

x^2 -12x + 36 + y^2 = 36

x^2 + y^2 = 12x

r^2 = 12rcos(theta)

r = 12 cos(theta)