Simplify this expression: 3x + negative x + 4 (8x÷2)
$$3x + -x + 4 (8x\div 2)\\ =3x + -x + 4 *(4x)\\ =3x + -x + 16x\\ =3x \;-\;x + 16x\\ =3x \;-\;1x + 16x\\ =(3-1+16)x\\ =18x\\$$