Hey Jin... from the beutiful city of Shah Alam ( Malesia)......

the problem you posted is very easy ...it seems to me that you have no idea what is all about....

Anyway put t =0 in the first equation and you will get the vector r1=0 this means that at t=0 it leaves the harbor....

at the same time the vector of the boat is r2=10i+8j get the magnitude of this vector and you will get |r2| =sqr(10^2+ 8^2)=10.8 Km ....as simple as such...

for the second question : the vector can be written r1=t(12i+16j) or r1=tv where v=12i+16j and this is the vector of the speed for the cargo vessel....now grt the magnitude of this vector |v|=sqr(12^2+16^2)=20 km/h

do the same for the Boat to find 5km per hour.

Please study this chapter more