Ответ:
Вот))))))))))))))))))
a₁ = 3 a₂ = 7
a₂ = a₁ + d
d = a₂ - a₁ = 7 - 3 = 4
d = 4
a₁₁ = a₁ + 10d = 3 + 10 * 4 = 3 + 40 = 43
a₁₁ = 43