A=<4.60,7.20>
b=<5.10,2.70>
The scalar product, or the inner product, or the dot-product, is by summing the products of the respective directions,
a.b=4.6*5.1+7.2*2.7
=23.46+19.44
=42.9
Lucas equation for his location is x(t) = 13t.
Alfonso's equation is x(t) = 238 - 21t
If you equate these, you get:
13t = 238 - 21t =>
34t = 238
t = 7
So after seven hours they meet.
40,000 cause 4x10 is forty and then add the zeros