To calculate the total amount Samuel spent at the farmers market on both days, we can break down the purchases made on each day.
First Day:
- He bought 3 pounds of apples at \( x \) dollars per pound, so he spent \( 3x \) dollars on apples.
- He also bought 2 bags of spinach at \( y \) dollars each, so he spent \( 2y \) dollars on spinach.
- Total spent on the first day: \[ 3x + 2y \]
Second Day:
- He bought 5 pounds of apples at \( x \) dollars per pound, so he spent \( 5x \) dollars on apples.
- He also bought 3 bags of spinach at \( y \) dollars each, so he spent \( 3y \) dollars on spinach.
- Total spent on the second day: \[ 5x + 3y \]
Now, we add the total spent on both days: \[ (3x + 2y) + (5x + 3y) = 3x + 5x + 2y + 3y = 8x + 5y \]
So, the expression that represents the total amount he spent at the market on both days is: \[ \boxed{8x + 5y} \]