1C, (½(-6+2),½(6-8))=(-2,-1).
2A, AB=-2-(-5)=-2+5=3;
AC=2-(-2)=2+2=4;
BC=√(AB²+AC²)=√(9+16)=√25=5; (Pythagoras)
Perimeter=AB+AC+BC=12.
3B, √((8-3)²+(8-2)²)=√(25+36)=√61=7.8 approx.
4D, 5√(36+25)=5√61=39.1 miles approx (40 miles).
5D, (2×9-10,2×8-10)=(8,6).