I assume the expression is:
2x2 - 8x
which factors to:
2x(x-4)
You can't "solve it" because you don't have an equation (equations have equal signs). For example, here's a common equation for this problem:
2x2 - 8x = 0
2x(x-4) = 0
Apply the "Zero Factor Property" to get x = 0 and x = 4 as the answers.