I need to know what I can get on my final to get a test average of 75%

Question

Test 1 

score 83% 

25% of grade 

 

Test 2 

score 74%

25% of grade 

 

Test 3 

score ?

30% of grade 

 

I need a 75% test average overall to pass 

Answer 1

NO

 

There must be a 4th exam worth 20% of the grade.

The percentages given add up to 80%. There's 20% missing.