How many ways are there to distribute n distinct balls into r boxes (a box can contain any number of balls, ranging from zero (none) all the way to all n balls)?

15 point ! ~ see if you know the answer to both you!

How to solve a simultaneous equation involved with fractions?

List x1, x2, x3, x4 where xi is the left endpoint of the four equal intervals used to estimate the area under the curve of f(x) between x = 4 and x = 6. a 4, 4.5, 5, 5.5 b 4.5, 5, 5.5, 6 c 4.25, 4.75, 5.25, 5.75 d 4, 4.2, 5.4, 6