A man earns x% on the first Rs. 2,000 and y% on the rest of his income. If he earns Rs. 700 from income of Rs. 4,000 and Rs. 900 from if his income is Rs. 5,000, find x%.

1. 10%
2. 15%
3. 20%
4. 25%

When total income is Rs. 4000, a man earns x% on first Rs.2000 and y% on Rs.2000.

2000x/100 + 2000y/100 = 700

When total income is Rs. 5000, a man earns x% on first Rs.2000 and y% on Rs.3000.

2000/100 + 3000y/100 = 900

The equations can be simplified to

x + y = 35 and 2x + 3y = 90

Solving these two equations simultaneously, x = 15%.

The correct option is B.