Simultaneous Equations and Mean of 3x and 6y

[pck2103]

What is the average of of 3x and 6y

1.) x + 2y = 7
2.) x + y =5

I used both equations to find the values of x and y by substitution. My book
says I only need equation 1 to figure out the answer that you wouldnt need
both equations.

How is this?

Thanks.

 

[pka]

Re: Simultaneous Equations and Mean

\(\displaystyle \begin{array}{l} x + 2y = 7 \\ 3x + 6y = 21 \\ \frac{{3x + 6y}}{2} = ? \\ \end{array}\)