Can someone answer #13, #15, and #16

#13: b
#14: c
#16: c

It is very easy, have a nice day :)

16). Volume of a cube: v = s³         (s) stands for side length

v = 3³
v = 3 × 3
v = 9

You were right, the answer is a.

 
I drew a picture to figure out this problem. I drew a circle with 16 different sections. Half of them were black and the other half were white. If a dart is thrown 3 times and lands on the black each time, then you have to eliminate the 3 times. So on the picture, eliminate 3 black blocks. The question wants to know the probability of the dart landing on a black if it's thrown a fourth time. In order to find this out, you need to eliminate just one more black section. Then, you have four more black sections left. You have to put 4 over the number of total black sections there were, which are 8. 4/8 = 1/2, so the final answer is 50%. Sorry if this is confusing. 

Step 1: 6x-10=1; step 2: 6x=11