Step-by-step explanation:
[tex]area \: of \: triangle = \frac{1}{2} \times 6 \times x \\ \\ \therefore \: 12 = 3 \times x \\ \\ \therefore \: x = \frac{12}{3} \\ \\ \: \: \: \: \: \: \: \: \huge \purple{ \boxed{\therefore \: x = 4}}[/tex]
