Wow, a lot a questions! I feel like I'm taking an exam!

(By the ways, you should use the search function above to check to see if someone has posted your question before. Just type in all of the key words to the problem in the search box.)

Anyways...

The answers are listed according to the name of the images:

Gmat 13:
See this post: https://www.beatthegmat.com/gmat-prep-to ... 12040.html


Gmat 7:
Since the triangle is an equilateral triangle, arc ABC is 2/3 of the circumference. So the circumference = 36.

Remember that the formula for circumference is C = D(pi). So far you have 36 = D(3.14). Solve for D. D is approximately 11.

Gmat 2:
4+y=-5 ==> y = -9
4+z=m

e+y=n ==> e=n+9
e+z=10 ==> n+9+z=10 ==> n+z=1 ==> n+m-4=1
==> n+m=5

Gmat 30:
(1) INSUFFICIENT: There is no way of knowing if these are the only two tollbooths, or if there are many more.

(2) INSUFFICIENT: There is no way of knowing the distance between the tollbooths. Could be greater than 10 miles, or less than.

(1) & (2): SUFFICIENT: If the first and last tollbooths are 25 miles apart, and there are 4 tollbooths, there has to be a pair of tollbooths less than 10 miles apart. You can check this by trying the find the distance between the tollbooths if they are evenly-spaced apart. 25/4 = 6.25 < 10. So the maximum that the tollbooth can be apart is 6.25 miles, before it start come closer to another tollbooth.

Gmat 18:
https://www.beatthegmat.com/difficult-fu ... 18216.html

Gmat 15:
https://www.beatthegmat.com/standard-dev ... t9116.html

Gmat: 33
https://www.beatthegmat.com/gmat-prep-sd ... 11712.html