please help me-- this question's a bit lengthy so ill say the rest in the comments, its concerning grading systems

Question

arbyj · Answer

test grades: 70, 87, 97
hw grades: 90, 85, 70, 94, 87, 78
particip. grades: 94, 95, 100 99

test avg: 50%
homework: 20%
par.: 10%
final exam: 20%

its asking to calculate the lowest grade i can score on my final to get a 90 for the course, how do i calculate it?

vuriffy · Answer

If only I was a teacher and had their program and just type all this in real quick. Haha. >.<

vuriffy · Answer

I have to get off soon, but it says test avg: so I would assume you would want to calculate that value to prepare to work out this question fully. 
70 + 87 + 97 = 254/3(amount of tests) = 84.66[repeated](test avg)

arbyj · Answer

no i already have it, those percentages make up my final grade

arbyj · Answer

my teacher has us set it up like this:

arbyj · Answer

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