Please find the missing number for this surface answer! I will mark brainiest if correct! 1.

Answer:
2
Step-by-step explanation:
[tex](2 * 6x) + (2 * 7x) + (2 * (6 * 7)) = 136[/tex]
[tex]12x + 14x + (2 * 42) = 136[/tex]
[tex]12x + 14x + 84 = 136[/tex]
[tex]12x + 14x = 136 - 84[/tex]
[tex]26x = 52[/tex]
[tex]x = 2[/tex]