Answer: 3 square inches.
If the park is 25 square miles, it could be 5×5 miles. If the scale is 1 inch = 5 miles, that would be 1×1 inch or 1 square inch on the map. Since 75 is 3×25, it will be 3×1 square inches on the map.
Step-by-step explanation: Remember that the scale represents linear measurements. For area, you must square the linear "sides" to get the number of actual square units represented by a square unit on the map.