We know 1 pound = 16 oz. If we want to find out how many ounces are in 320 lbs, we must multiply 16 by 320 = 5120 ounces. Now we must divide by 12 to see how much she ate per month. 5120 divided by 12 is 426.667 or 426 and 2/3 ounces per month.
Alternatively, we can set up a proportion 1 lb / 16 ounces = 320 lb / x ounces. We cross multiply 1 times x = 320 times 15. On the left hand side we just have x and on the right hand side we get 5120. Hence, x=5120 ounces per year. To find how many she ate per month we must divide by 12 since there are 12 months in a year. So it comes out to 426 and 2/3 ounces per month.
