-6+b=-5，-2a-3=-5

b= 1，a= 1

So the two straight lines are y=3x+ 1 and y=x-3 respectively.

Because the topic requires images, you can draw two straight-line images, and then find the solution set of x with y=3x+ 1 above the image with y=x-3 (without taking the intersection point).

The final solution set is (-2, +∞).