If is the first term in the series, then the next term is for some fixed , the term after that is , and so on. So the 20th term in the series would be .
X=750+125.75x subtract to variable (x) on one side x-125.75x=750+125.75x-125.75x -124.75x=750 divide -124.75 to get variable (x) by itself -124.75x/-124.75=750/-124.75 x=-3000/499 or x=-6 6/499 or x=-6.01202