Hey there!
We can find the answer to this by finding how much is 3/4 of the sugar and subtracting that from the 20 pounds of sugar he started with.
3/4 in decimal form is 0.75, so we can multiply 20 by 0.75 to get 3/4 of 20.
0.75 x 20 = 15
This means 3/4 of the sugar is 15 pounds.
Now we can subtract that from the original 20 pounds he started with.
20 - 15 = 5
He has 5 pounds of sugar left.
Hope this helps!