Read the following Passage. Understand the Mathematical concept in it and answer the questions that follow. Each question carries 1 score.
The common difference of the arithmetic sequence 15,14,13,12,...... is `14-15=-1`. First terms of the sequence is 15 and the 15th term is `15+14x-1=15-14=1`.
Similarly the 4th term is 12 and the `12^(th)` term is 4. Its 16th term is, `x_(16)=15+15x-1=15-15=0`. So the sum of the first 31 terms is also zero. that is if the `n^(th)` is m, then the mth term is n and the `(m+n)^(th)` term is zero.
Seventh term of an arithmetic sequence is 10 and the `10^(th)` term is 7. What is the common difference?