Susan's math teacher assigned x homework problems on monday. on tuesday, she assigned 13 more problems. over the two days, a total of 21 homework problems were assigned. which equation could be used to find x, the number of problems assigned on monday?
a. x - 13 = 21
b. x + 13 = 21
c.21 + x = 13
d.13x = 21

Aplane is taking off from bangladesh headed to new york city. at the same time, a plane from new york city is headed to bangladesh is also taking off. the plane bound to new york city is traveling at 600 mph, while the plane traveling to bangladesh is traveling at 400 mph. how far from new york city will the two planes meet if the distance between new york city and bangladesh is 8,000 miles?

In the xy-plane, if the parabola with equation passes through the point (-1, -1), which of the following must be true?

There are three bags: a (contains 2 white and 4 red balls), b (8 white, 4 red) and c (1 white 3 red). you select one ball at random from each bag, observe that exactly two are white, but forget which ball came from which bag. what is the probability that you selected a white ball from bag a?