First lets write out the equation:
-8x + 2x - 16 < -5x + 7x
Lets collect the x values
-6x - 16 < 2x
-8x - 16 < 0 (subtract both sides by 2x to get all the x's on one side)
-8x < 16 ( add both sides by 16 to get all the x's alone)
x < -2 ( divide both sides by -8 to get what just x is)
So x < -2