Answer:
13
Step-by-step explanation:
You have to construct an equation to solve this. The equation has all the weights of the packages plus x over eight. Set this equal to 12.
You set up the equation like this because you are essentially calculating an average backwards. Usually, you know all the numbers, and you have to find the average. In this case you know the average but not all the numbers.
You add up all the numbers like you would normally do when finding an average. Instead of dividing the sum of the weights by 8, multiply it by 12 to solve for x.
[tex]\frac{25+10+20+4+6+3+9+x}{8} =12\\83+x=96\\x=13[/tex]
The weight of the 8th package is 13.
