To find the total amount Samuel spent at the market on both days, we need to calculate the total for each day and then add them together.
On the first day, he bought:
- 3 pounds of apples at \( x \) dollars per pound: \( 3x \)
- 2 bags of spinach at \( y \) dollars each: \( 2y \)
So, the total spent on the first day is: \[ 3x + 2y \]
On the second day, he bought:
- 5 pounds of apples at \( x \) dollars per pound: \( 5x \)
- 3 bags of spinach at \( y \) dollars each: \( 3y \)
So, the total spent on the second day is: \[ 5x + 3y \]
Now, we add the totals from both days: \[ (3x + 2y) + (5x + 3y) = 3x + 5x + 2y + 3y = 8x + 5y \]
Thus, the expression that represents the total amount he spent at the market on both days is: \[ \boxed{8x + 5y} \]