I figured this out using each of the supplements one at a time. For calcium, Brand A gives you 5mg per spoon and Brand B gives you 4 mg per spoon. If you need 24 mg of calcium per day, divide 24 by each of those amounts per spoon. If you use Brand A, you need 24/5 = 4.8 (our first x value), and if you use Brand B, you need 24/4 = 6 (our first y value). Let's simplify that to (4, 6). That exists is a ratio of 2:3, so the x and y coordinates would be (2, 3) which is in fact a choice up above. Do the same for the Iron for A and B. 15mg needed/4mg per spoon in A = 3.75 (our second x value) and 15mg needed/6mg per spoon in B = 2.5 (our second y value). Simplify that down as well by rounding to (3, 2) which is also a choice. The last one, vitamins: 16mg needed/7mg per spoon in A = 2.2 (our last x value), and 16mg needed/4mg per spoon in B = 4 (our last y value). That can be rounded and simplified to a ratio of (1, 2) but that is not a choice. So... that's what I have! Hope it helps!
