The silver coin is the highest among the given treasures on the number line.
To locate the treasures on the number line, we can arrange them in ascending order:
Gold coin: -7/4 feet
Bronze coin: -1/4 feet
Silver coin: 3/2 feet
Copper coin: -11/4 feet
Now, we compare these values:
Copper coin is the lowest at -11/4 feet.
Gold coin is next at -7/4 feet.
Bronze coin is at -1/4 feet.
Silver coin is the highest at 3/2 feet.
So, the silver coin is the highest among the given treasures on the number line.