So I was eating a piece of bread and my dog wanted some, and I then wondered how I would determine how we could share the bread equally, but in relation to each others' sizes. I figured it would be a ratio problem, but not of the typical sort. For the exercise of this problem, I set the amount of bread at 10 bites. I know my dog weighs 13lbs. and I weigh about 180lbs. So, what I did was take our total weight (180 + 13 = 193) and placed that over the total bread weight and did a ratio of the totals against my weight. 193/10 = 180/x. I found out x was ~9.3264 (good enough for our purposes). Using simple subtraction I learned what his portion would be: 0.6735 bites. I checked by dividing our weights (180/13=13.846) against my new found ratio (9.3264/.6735=13.847) and they matched.
Did I do this right? Also of note I haven't done math besides addition and subtraction in about five years.