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Let a be first term
[tex]\\ \rm\longmapsto a_8=a+7d[/tex]
[tex]\\ \rm\longmapsto 26=a+7(3)[/tex]
[tex]\\ \rm\longmapsto a=26-21[/tex]
[tex]\\ \rm\longmapsto a=5[/tex]
Now
[tex]\\ \rm\longmapsto a_4=a+3d[/tex]
[tex]\\ \rm\longmapsto a_4=5+3(3)[/tex]
[tex]\\ \rm\longmapsto a_4=5+9[/tex]
[tex]\\ \rm\longmapsto a_4=14[/tex]