Final answer:
The question is a middle school level mathematics problem involving unit conversion and area calculation. The area of a 20-foot by 13-yard garden, after converting yards to feet, is 780 square feet. option c is correct.
Step-by-step explanation:
The subject of the question appears to be Mathematics, specifically it deals with converting units of measurement and calculating areas. The mention of a vegetable garden suggests the student is working on a real-life application of math involving measurements of length and area.
The question seems to be at a Middle School level as it requires basic skills in arithmetic and unit conversion. To find the area of the garden in square feet, one must first ensure that both dimensions are in the same unit. In this example, one dimension is given in feet and the other in yards, so a conversion is necessary.
There are 3 feet in a yard, so multiplying the length in yards (13) by 3 gives the length in feet (39). The area of the garden is then calculated by multiplying the length by the width (20 feet), resulting in 780 square feet (20 feet × 39 feet = 780 square feet).