[tex]\it 1)\ \ -2x+20<0 \Rightarrow -2x<-20|_{\cdot(-1)} \Rightarrow 2x>20|_{:2} \Rightarrow x>10 \Rightarrow x\in(10,\ \infty)\\ \\ 2)\ -2x+20\geq-x+15 \Rightarrow 20-15\geq-x+2x \Rightarrow 5\geq x \Rightarrow x\leq5 \Rightarrow x\in(-\infty,\ 5][/tex]
