(1) Jacks hourly wage was 5$/hr more than Mark
Let x be mark's wage/hr then jacks=x+5
Difference after 6% increase will be = (x+5)*(106/100)-x*(106/100)
where the variable x cancels out and we get the answer.... (1) is sufficent
(2)Jack:mark =4:3
let x be total wages then Jack's =4x/7 mark's = 3x/7
After 6% increase difference = (106/100)*(4x/7-3x/7)... we hv no other info therefore (2) is insufficient
ans A

Let M be Mark's wage/hr and J be Jacks wage/hr
We need to find out J -M

Given that J and M had a 6% increase in wage/hr.
So wages per hr will be 1.6J and 1.6M.

Stmt1:
Before increase
J = M +5
=> J-M = 5 ------------ 1
After the increase we have.
1.6J - 1.6M = ?
= 1.6(J-M) ------------ 2
Substituting 1 in 2
= 1.6 * 5
Sufficient.

Stmt 2.

J/M = 4/3.
J = 4M/3.

After the increase, we have
1.6J = (1.6 *4 * M)/ 3
1.6J = 1.6 * 4M/3

We cannot find J -M.. Hence insufficient.

So A

You can even substitute values

Lets take the before wage increase salary of Jack as 10 and Mark as 5.

After considering 6% wage increase, the sal of Jack would be 10.6 and that of Mark would be 5.3

You can substitute any number for Mark and a value which is 5 units greater than Mark for Jack..you will get the same difference...

So, you can find the difference and hence A is sufficient...

W.R.T statement 2) we know only the ratio of Jack to Mark as 4:3, but not the actual values...

So insufficient...

Hence A.