So you start with a 88.1%.
Here is how I figure it...
If you get a 15 out of 15 on an assignment, that would be a 100% for your assignment grade.
You take 100% and add it to your 88.1% and you get 188.1%. That doesn't seem reasonable for a grade though does it...
So you take that 188.1% and you divide it by 2 (divide it in half) and you get 94.05%.
So if you get 15 out of 15 on your assignment your grade will go up to a 94.05% as I figure.
Word problem:
15 out of 15= 100%+88.1%= 188.1%÷2= 94.05%
Your final grade as I figure would be a 94.05%