Answer:
- you - 4 rocks and 16 fossils
- friend - 12 rocks and 8 fossils
Explanation:
Let the rock be r and the fossil be f
Equations
- You: r + f = 20
- Friend: 3r + 1/2f = 20
Double the second equation and subtract the first one:
- 2(3r + 1/2f) - (r - f) = 2*20 - 20
- 6r - r = 20
- 5r = 20
- r = 4
Then find f:
So you collect 4 rocks and 16 fossils
Friend collects:
- 4*3 = 12 rocks and
- 1/2*16 = 8 fossils