I don't understand why: 3(x + 4) = 11x?

It doesn't.

3(x+4) = 3x + 12.

3(x+4) could only be 11x if x was 1/2.

Okay,
3x+12=11x,
12=11x-3x,
12=8x,
x=12/8.

3(x+4)=3x+12
=11x

then 3x+12=11x

11x-3x=12
8x=12
x=12/8=3/2


when x=3/2 , it can satisfy the equation

3(x + 4) = 11x
3*x + 3*4 = 11x
3x + 12 = 11x
3x - 11x = -12
-8x = -12
x = -12/(-8)
x = 3/2 (1.5)

3 x + 12 = 11 x
12 = 8 x
x = 12 / 8
x = 3 / 2

3(x + 4) = 11x
3x + 12 = 11x
3x - 11x = - 12
- 8x = - 12
x = 12/8 or 3/2.

to check the answer:

3(3/2) + 12 = 11(3/2)
9/2 + 12 = 33/2
4 1/2 + 12 = 16 1/2
16 1/2 = 16 1/2.

or, 3x +12 =11x
or, 3x+12-11x=0
or, - 8x = -12
or, 8x= 12
or, x=12/8
or, x=6/4
or, x = 3/2
i.e x= 3/2

I'm pretty sure its asking you to FIND x, not that the answer is really 11x.

3(x+4) = 11x
3x+12 = 11x
12 = 8x
x = 12/8 or 3/2

x= 3/2

not sure but i thought that 3(x+4) meant 3 multiplied by x and then by 4 so something like this would be the answer(if i am right :))

3x+12