If the total number of bikes sold in 2009 was 50000, then by what number was the sales of white bikes less than that of yellow and red bikes put together?

Given 

total no. of bike sold in 2009 =50000

from graph

No. of red bike sold in 2009=20%

NO. of yellow bike sold in 2009=10%

NO. of White bike sold in 2009=25%

$$25\% of 50000=\frac{25}{100}\times50000$$

$$25\% of 50000=25\times500$$

$$25\% of 50000=12500$$

NO. of White bike sold in 2009=12500

total bike together yellow and red= 30%

$$30\% of 50000=\frac{30}{100}\times50000$$

$$30\% of 50000=30\times500$$

$$30\% of 50000=30\times500=15000$$

total bike together yellow and red=15000

Required (Yellow+red)-White= 15000-12500=2500