-(t-s-(-a))+(-n+p)
m-(x-p+m)
(a+b)-(a-b)
-(t-s-(-a))+(-n+p)=-t+s-a-n+p
m-(x-p+m)=m-x+p-m=p-x
(a+b)-(a-b)=a+b-a+b=2b