Ok, thank you. That looks like a good source. I appreciate it. I guess I was just adding to the fact that the

Gmatclub tests are often times, not written well. One example of many:

m03 #29.

"A computer generated a

consecutive set of numbers using the following formula:

where is the common difference between any two consecutive numbers of set .

If the sum of the second and the fifth number in the set is 8, and the sum of the third and the seventh number is 14, what is the first number in set ?" (the interval was 2 units).