If 8 SSB or 12 CISF companies can patrol the Indo-Tibet border in 3 days, then how long will 6 SSB and 9 CISF companies take to do the same?

First, let's understand the rate at which the SSB and CISF companies can patrol the Indo-Tibet border.

According to the question, 8 SSB companies can patrol the border in 3 days. So, the rate at which SSB companies work is 8 companies/3 days = 2.67 companies/day.

Similarly, 12 CISF companies can patrol the border in 3 days. So, the rate at which CISF companies work is 12 companies/3 days = 4 companies/day.

Now, we need to find out how long 6 SSB and 9 CISF companies will take to patrol the border.

The combined rate of 6 SSB and 9 CISF companies is (6/2.67) + (9/4) = 2.25 + 2.25 = 4.5 days.

So, 6 SSB and 9 CISF companies will take 4.5 days to patrol the Indo-Tibet border.