Let's start by setting up a system of equations based on the given information:
A + F = 64 (equation 1)
A = 3F (equation 2)
where A is the number of rocks in Arthur's collection and F is the number of rocks in Fernando's collection.
We can use equation 2 to substitute A in equation 1:
3F + F = 64
Simplifying, we get:
4F = 64
Dividing both sides by 4, we get:
F = 16
So Fernando has 16 rocks. To find the number of rocks in Arthur's collection, we can substitute this value into equation 2:
A = 3(16)
Simplifying, we get:
A = 48
So Arthur has 48 rocks.