jmc

We expand each product separately: $$\begin{array}{rl}(2x-5)(x+7)& =2x(x)+2x(7)-5(x)-5(7)\\ & =2x^2+14x-5x-35\\ & =2x^2+9x-35\end{array}$$and $$\begin{array}{rl}(x+5)(2x-1)& =x(2x)+x(-1)+5(2x)+5(-1)\\ & =2x^2-x+10x-5\\ & =2x^2+9x-5.\end{array}$$So, we have $$\begin{array}{rl}& (2x-5)(x+7)-(x+5)(2x-1)\\ & =2x^2+9x-35-(2x^2+9x-5)=\boxed{-30}.\end{array}$$