From the sequence given 3,7,11,15,19
first term (a) = 3
common difference(d) = 4
Hence to find the nth term, the expression is given as shown below
[tex]\begin{gathered} T_n\text{ = a + (n -1)d} \\ T_n\text{ = 3 + (n - 1)4} \\ \text{ = 3 + 4n -4} \\ \text{ = 4n - 4+ 3} \\ \text{ = 4n - 1} \end{gathered}[/tex]To find the 20th term, we have
[tex]\begin{gathered} T_n\text{ = a + (n -1)d} \\ a\text{ = 3, d = 4},\text{ n = 20} \\ T_n\text{ = a + (n -1)d} \\ T_n\text{ = 3 + (20 - 1)4} \\ T_{20}\text{ = 3 + (19)4 } \\ T_{20}\text{ = 3 +76} \\ T_{20}\text{ = 79} \end{gathered}[/tex]
