11) The bottom triangle is 30 60 90 triangle and the top triangle is a 45 45 90 triangle. So we can figure out the 3 sides of the bottom triangle to be 6, 6sqrt(3), and 12. So that means x is just 6sqrt(3) * sqrt(2) = 6sqrt(6)
12) The left triangle is a 30 60 90 triangle and the right triangle is a 45 45 90 triangle. The right triangle has sides 6sqrt(3), 6sqrt(3), 6sqrt(6). So that means the 3 sides of the the left triangle is 6, 12, 6sqrt(3).
So x is 12 in this case.