How do I estimate a single score from two different sets of score each with different denominator?

#1
I wanted to have a combined score for a students test.
18 student have written three different tests. First test has 10 maximum marks, second test has 15 maximum marks, third test has 170 maximum marks.
 

fed2

Active Member
#2
should a test with more marks recieve more weight when computing the single score (presumably an average)?