Do you have one assignment and two marks?
For what i understand, if your first test was worth 40 points and you got 67% it means you got 26.8/40 (67x40/100)
for the second one which is worth 60 points, you got 73% it means that you got 43.8/40 (73x60/100)
so your overall mark is 26.8+43.8=70.6
this mark is on 100 so you have 70.6% as an overall mark
hope i've helped a little bit
Sue