The midterm is 15% so in turn, that means 85% of the class is done prior to the midterm.
This means that you scored 97% of that 85% so far.
Written in mathematical terms, that looks like this:
.97*85 = 82.45%
82.45% is what you have before the midterm starts.
Next, it says you scored 60 on the midterm. Since the midterm is 15%, it looks like this in math terms:
.6*15 = 9%
Your final grade therefore, will be:
82.45+9 =91.45%
(this is without rounding or any curves)