GMAT Math

can someone explain these problems please? I dont get them[/img]

problem #99, 156 and 171 sorry i did not write that on the commebt

jeph86 wrote:What is the value of (2t + t - x)/(t - x)

(1) 2t/(t - x) = 3

(2) t - x = 5

Statement 1:

Statement 1 gives us a value for 2t/(t - x).

The expression in the question can be manipulated to 2t/(t - x) + (t - x)/(t - x) = 2t/(t - x) + 1

Using the value given by Statement 1, we get 2t/(t - x) + 1 = 3 + 1 = 4

Sufficient.

Statement 2:

We can use Statement 2 to substitute 5 where we see t - x in the expression.

(2t + 5)/5

However all Statement 2 tells us really is that t and x are 5 apart. So t could be any number, and the expression could take any value.

Insufficient.

The correct answer is A.