Question 1:

(1) Let Jack's hourly wage is $J and Mark's hourly wage is $M.
J = M + 5
Both received an hourly wage increase of 6%, so Jack receives 1.06(M + 5)
After 6% increase, Mark receives 1.06M
Difference in their wages = 1.06M + 1.06(5) - 1.06 M = 5.3
So, (1) is SUFFICIENT.

(2) Let Jack's hourly wage = 4w and Mark's hourly wage = 3w
Both received an hourly wage increase of 6%, Jack receives 1.06(4w) = 4.24w and Mark receives 1.06(3w) = 3.18w
We find their difference but there id no information on how to find w.
So, (2) is NOT SUFFICIENT.

The correct answer is [spoiler](A)[/spoiler].

Question 2:

Let M be the number of males and F be the number of females.

(1) 0.33M + 0.20F were transferred from another college, which is NOT SUFFICIENT to answer the question.

(2) 25% of (M + F) = 0.25(M + F) were transferred from another college, which is NOT SUFFICIENT to answer the question.

Combining (1) and (2), we get 0.33M + 0.20F = 0.25(M + F) or 0.08M = 0.05F or M = 0.625F, solving which we'll get the answer to the question.

The correct answer is [spoiler](C)[/spoiler].

Question 3:

Let W be the number of women and C be the number of children.
Then W:C = 5:2 or C = 2W/5
Let the number of men be M.

(1) C:M = 5:11 or M = 11C/5, which is NOT SUFFICIENT to answer the question.

(2) 2nd statement is NOT SUFFICIENT as gives no information on the no. of men.

Combining (1) and (2), we get, W < 30 and M = 11C/5 = 22W/25 (Putting C = 2W/5 in M = 11C/5)
Now, M = 22W/25 and W < 30 implies that the only possible value of W = 25 as it has to be an integer which also should be multiple of 25.
Since we know W = 25, we can find M.

The correct answer is [spoiler](C).[/spoiler]

Does that help?