3 log₁/₇ x = log₁/₇ 9 + log₁/₇ 3
3 log₁/₇ x = log₁/₇ (9 * 3)
3 log₁/₇ x = log₁/₇ 27
log₁/₇ x³ = log₁/₇ 27
x³ = 27
x = 3
Ответ: 3