Sam charges $3 per week to care for house plants while the owners are out of town. he had six customers in one two-week period. he saved one-fifth of his earnings. how much did he spend?

This is so hard and it’s for a test

Abag contains 4 red, 7 blue and 5 yellow marbles. event a is defined as drawing a yellow marble on the first draw and event b is defined as drawing a blue marble on the second draw. if two marbles are drawn from the bag, one after the other and not replaced, what is p(b|a) expressed in simplest form? a. 7/16 b. 7/15 c. 14/16 d. 14/15

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?