54 + 6 + 2(8 - 3 x 4)

We must do inside the parentheses first. In the parentheses, there are a
subtraction and a multiplication.  We must do the multiplication 3 × 4
first, replace it by 12, and copy everything else over:

54 + 6 + 2(8 - 12) 

We must do inside the parentheses first.  In the parentheses, there is only
a subtraction.  We do the subtraction 8 - 12, replace it by -4, and copy
everything else over:

54 + 6 + 2(-4)

There is nothing to do inside the parentheses, so we look left to right for
a multiplication or division.  There is only a multiplication.  We do the
multiplication 2(-4), replace it by -8, which must go inside parentheses to
keep two signs from coming together, and copy everything else over:

54 + 6 + (-8)

We do additions left to right, so we do 54 + 6 and replace it by 60 and copy
everything else over:

60 + (-8)

That's just

52

Edwin