Question 25038
For the first one.
It reallly easy.
Use the formula.
a^2+b^2=c^2
a= 3, b=4
9+16=c^2
c=5


The second one is really easy too.
Use pythagoras Theorem.
35^2+b^2=65^2
find b
65^2-35^2=b^2
b^2=3000
Take a squre root.
b=54.8


Hence you are 54.8km from starting point 
Paul.