Concept: The question tests on the basics of Counting
Solution:
Let the number of cards that Mushtaq has = M and the Number that Iqbal has = I
Let the number of cards given either ways be = n
If Mushtaq gives Iqbal n cards, then Iqbal has I + n cards and Mushtaq has M - n cards
Given that I + n = 4 * (M - n) ... (1)
If Iqbal gives Mushtaq n cards, then Iqbal has I - n cards and Mushtaq has M + n cards
Given that I - n = 3 * (M + n) ... (2)
Adding (1) and (2), we get 2I = 4M - 4n + 3M + 3n
2I = M - n ... (3)
Subr=traction (2) from (1), we get 2n = 4M - 4n - 3M - 3n
2n = M - 7n
M = 9n
Substituting in (3), we get 2I = (7 * 9n) - n = 62n
Therefore I = 31n
The number of cards Iqbal has will be a multiple of 31 and only option B satisfies the same.
Option B