please help! really needing help solve the problem

Answer:
7
Step-by-step explanation:
By Basic proportionality theorem:
[tex] \frac{10}{8} = \frac{3x - 6}{12} \\ \\ \frac{10 \times 12}{8} = 3x - 6 \\ \\ \frac{120}{8} = 3x - 6 \\ \\ 15 = 3x - 6 \\ 15 + 6 = 3x \\ 21 = 3x \\ \frac{21}{3} = x \\ 7 = x \\ \\ \huge \red { \boxed{x = 7}}[/tex]