Linear yield questions like this are really just compounding fractions. I like to think of it this way.
Lets say you have a recipe for fruit salad, and it calls for cored apples. When you make the fruit salad, you lose an amount, say five percent, of the apple. Then, you decide to use the fruit salad in a jello recipe. In the process, you spill some of the fruit salad, say another five percent. If you take the initial apples at 100%, make fruit salad at 95%, then make the jello at 95%, you can compound the yields. 100%*95%*95%=90.25%.
Now with the chemistry, it's the same thing. Just multiply the percentages.
After the overall reaction, you will have a yield of 80.3%.