For each of the following $A.P.s$,find the $n^{th}$ term: $10.5, 11.7, 12.9, 14.1, \dots$

Find the number of terms in the finite $A.P.$ $7, 11, 15, \ldots, 107$.

$A$ person has to clear a debt of $Rs. 3250$ by monthly instalments. In the first month he has to pay $Rs. 20$ and then onwards every instalment is $Rs. 15$ more than the previous instalment. How long will it take to clear the debt?

Find the $12^{th}$ term of the $A.P.$ $9, 13, 17, 21, \ldots$

For the $AP: -3, -7, -11, \ldots,$ can we find $a_{30} - a_{20}$ directly without actually finding $a_{30}$ and $a_{20}$? Give reasons for your answer.

For the $A.P.$ $0.1, 0.4, 0.7, 1, \ldots,$ the common difference is.........