Verified answer

[tex]\displaystyle\bf\\a_{1} =80\\\\a_{2}=195\\\\n=24\\\\d=5\\\\a_{24} =a_{1} +23d=80+23\cdot 5=80+115=195\\\\\\S_{24} =\frac{a_{1}+a_{24}}{2}\cdot 24=(a_{1} +a_{24} )\cdot 12=(80+195)\cdot12=\\\\\\=275\cdot 12=3300\\\\\\Otvet: 3300[/tex]