<p>I don't understand why you would multiply the total of marbles by the average cost. Isn't the average cost not exact? How will you get the exact total cost by multiplying the total marbles with average cost?</p>

<p>Look, there are 3 bags total right?
The 3 bags each have a certain amount - 20, 50 and 100 marbles.
To find the average cost per marble you need to divide the total combined cost for all 3 bags of marbles by Total number of marbles </p>

<p>You get this equation: (2+4+x)/(20+50+100) = .08 Solve for X</p>

<p>Well my key problem is the average cost per marble. The average isn't what each marble costs! It's just an average right?</p>

<p>So like, say you had 3 test scores. one was 70, was was 80 and one was 35.
The average of these is about 62%. But that's not was each test score was. IDK how to explain the way i'm reasoning it..</p>

<p>Yes, but I was looking at the average of the costs of ONE piece from each bag. That is to say, the average of the different costs of marbles.</p>

<p>If I didn't know the meaning of average, I would hardly be able to do that, would I? And if I didn't know English, I wouldn't be able to type this, would I?</p>