How mikrotik can be used to merge two broadband internet connection?

thnk u bro i got abslutly clear now on merging connections through mikrotik

It can't however it can load balance and alternate packets to both connections at the same time that gives an effect of increase speed on non session based TCP communication e.g. torrents. :)

there is a good guide for it here:

http://aacable.wordpress.com/2011/06/04/mikrotik-4-wan-load-balance-pcc-complete-script-by-zaib/

Thank you