Among the stamps that Eliot collected, 4/5 of them were local stamps and the rest were foreign stamps. After exchanging 20 local stamps for 20 foreign stamps, the number of local stamps that Eliot has becomes 8/15 of his total collection. How many local stamps did Eliot have at first?
+2666 Let \(l \) = local stamps and let \(f\) = foreign stamps.
We have the system:
\(l = {4 \over 5}(l + f)\)
\(l - 20 = {8 \over 15} (f + l) \)
Now, just solve for l and f...
