Why can i not combine the -12 and 3?

If 10 men take 18 days to mow 60 acres of grass, how long will 15 men take to mow 80 acres?

Find the value of ax 4 ; a = 2, x = 1. select one: a. 2 b. 4 c. 1 d. 8

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