common difference=d=43-39=4
We need first term a
[tex]\\ \sf{:}\dashrightarrow a_5=43[/tex]
[tex]\\ \sf{:}\dashrightarrow a+4d=43[/tex]
[tex]\\ \sf{:}\dashrightarrow a+4(4)=43[/tex]
[tex]\\ \sf{:}\dashrightarrow a+16=43[/tex]
[tex]\\ \sf{:}\dashrightarrow a=27[/tex]
