Hey there!
ANSWER: 
EXPLANATION:
To find the answer to your question, you will need to add.

First, multiply the denominator.

So the denominator will be 20.
Now move on to the numerator. Multiply 5 by 3.

Now multiply 4 bu 2.

If you want to get the numerator, add what you got after multiply.

The numerator is 23. So now let's complete the fraction.

This is your answer!
Hope this helps!

50x513 is 25,650, 25,650x2 is 51,300
Well.. 160 x 3 = 480. So he would've had to give only 2 bags. But he would've given a fraction of a bag, but if you're only talking whole numbers, then the answer is 2. If you're talking fractions, then the answer is 2.51875.
Look at some shorter periods of time to decide whether their reasonable. Do that by simplifying the fraction. . . . . 40,000 pounds / 80 years = 4,000 pounds / 8 years = 2,000 pounds (1 ton) / 4 years = 1,000 pounds / 2 years (have you decided yet ? Well, simplify it some more) 1,000 pounds / 2 years = 500 pounds per year = almost 1 and 1/2 pounds of bread every day of your life. NOW what do you think ? Make sense ?