SOLUTION: A student gets 70% in one subject, 80% in the other. To get an overall of 75% how much should get in third subject.

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Question 252808: A student gets 70% in one subject, 80% in the other. To get an overall of 75% how much should get in third subject.
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
(.70+.80+x)/3=.75
.7+.8+x=3*.75
1.5+x=2.25
x=.75=75%
we could also have reasoned that (.70+.80)/2=.75 already so he needs to get .75 (75%) to maintain the 75%