Assuming the x stands for multiplication... follow the ordering rules:
First let's take care of the exponents. 4²=16 and (-6)²=36. At the same time I will add some spacing between the terms:
3x16 - 36 + 4 - 6x4
Now do the multiplications:
48 - 36 + 4 - 24
The rest is just addition and subtraction
48 - 36 + 4 - 24 = -8