First with 20 pounds of apples to make 2 pounds of jam we know that.
So the we subtract 20-10=10, since we want 3 pounds we needed to split it because 3 is an odd number and if 20 apples in 2 pounds then with that we would have 40 pounds of apples for 4 pounds of jam.
So 10 multiplyed my 3 = 30
30 pounds of apples makes 3 pounds of jam.