First, we acknowledge that the equation that we need to solve will be "x+(x+1)+(x+2)=999" This is because x represents the smallest of three consecutive numbers whose sum is 999. Simplifying this equation will leave us with 3x+3=999 which is simplified further to 3x=996 and again simplified to x=332. X is the smallest number of the three.
It totally depends on the value of 'a', and if 'a' changes, then (6a-2) immediately changes too. Whatever 'a' is at the moment, (6a-2) is 2 less than 6 times 'a'.