I have a sequencing problem that I cannot find a way to solve using the three major formulas for finding sequencing elements.

The difference between terms is given (1/2). The sum of the terms is minus 105/2, and the last term is also given (0).

However, neither the first term nor the number of terms is given.

I cannot find a way to solve such a problem. All of the formulas seem to require both the number and the first term and/or the last term.

The answers given are: Minus 7 for the first term, and 15 as the number of terms.

If this is solvable, I would very much appreciate the formula sequence.

If not, I would like to know that as well.

Thanks so much.

Ron