He's 9 years old. :-)
In seven years, he'll be 16, and 16 is two times older than 8 - the age he was last year.
Answer:
There are 4 ounces of Fiber X cereal in the mix
Step-by-step explanation:
Lets n be the amount of ounces of Fiber X in the mix. Since there are a total of 12 ounces in the mix, then, on terms of n, there are 12-n ounces of Fiber Max on it.
Since 65% of the mix is Fiber, then there are 12*0.65 = 7.8 ounces of Fiber. We can also obtain this value if we take the proportions of Fiber in each cereal of the mix (in terms of n), so that we can obtain the true value of n
we have
7.8 = n *0.55 + (12-n)*0.7 = 0.55n + 8.4 -0.7 n = 8.4-0.15n
Therefore
0.15 n = 0.6
n = 0.6/0.15 = 4
As a consecuence, there are 4 ouces of Fiber X cereal in the mix.
The answer is (-x^2 - 3x +28)