Question 927167
<pre>

 8 x 1 - 2 =   6 
 6 x 2 - 3 =   9 
 9 x 3 - 4 =  23 
23 x 4 - 5 =  87 
87 x 5 - 6 = 429 

So, the next number is 429. 

Edwin</pre>