по определению логарифма ОДЗ x>0

log(2) x^3 = 3 log(2) x

log(8) x^7 = log(2^3) x^7 = 7*1/3 log(2) x

7/3 log(2) x = 14

log(2) x = 14/7 * 3 = 6

3*log(2) x = 3 * 6 = 18

ответ 18

Verified answer

log(8) x⁷ = log(2³) x⁷ = 7/3 log(2) x = 14

log(2)x = 14 * 3/7 = 6

log(2) x³ = 3log(2) x = 3*6 = 18