\(a,VT=-\left(23-a\right)+33\)
\(=-23+a+33\)
\(=a+\left(33-23\right)\)
\(=a+10=VP\)
\(b,VT=-\left(a-b\right)+\left(b-c\right)-\left(a-c\right)\)
\(=-a+b+b-c-a+c\)
\(=\left(b+b\right)+\left(-a-a\right)+\left(-c+c\right)\)
\(=2b-2a=VP\)
\(c,VT=-\left(-a+b+c\right)+\left(b+c-1\right)\)
\(=a-b-c+b+c-1\)
\(=-b+a-1+b+\left(-c+c\right)\)
\(=-\left(b-a\right)-\left(1-b\right)=VP\)
#Toru