Find the first term and the common difference of the arithmetic sequence whose $\displaystyle {7}^{\text{th}}$ term is $\displaystyle {14}$ and $\displaystyle {14}^{\text{th}}$ term is $\displaystyle {21}$.

First term is Preview Question 6 Part 1 of 2   ,
Common difference is Preview Question 6 Part 2 of 2