We have given [tex] t_{1}=3 [/tex] and [tex] t_{n} = t_{n-1} + 4 [/tex]. Fifth term is [tex] t_{5}= t_{4}+4 [/tex]. It means we need to find [tex] t_{4} [/tex] and in order to find the latter, we have to find [tex] t_{4}= t_{3}+4 [/tex], [tex] t_{3}= t_{2}+4 [/tex] and [tex] t_{2}= t_{1}+4 [/tex] . Since we know the value of [tex] t_{1} [/tex], beginning from the last equation we can find the value of [tex] t_{5} [/tex]. We can write that [tex]t_{2}= t_{1}+4=3+4=7[/tex], [tex]t_{3}= t_{2}+4=7+4=11[/tex] and [tex]t_{4}= t_{3}+4=11+4=15[/tex]. Since [tex] t_{5}= t_{4}+4 [/tex], then [tex] t_{5}= 15+4=19 [/tex]
