Answer:
4,300 square feet
Explanation:
First, calculate the area of Jayden's front yard. 
50 feet × 80 feet = 4,000 square feet 
 
Next, find the area of half of Jayden's back yard. 
1/2(20 feet × 30 feet) = 300 square feet 
 
Last, add the two areas together. 
4,000 feet + 300 feet = 4,300 square feet 
 
So, Jayden needs to purchase 4,300 square feet of sod