What is the value of y in the solution to the system of equations? x+2y=12x – 3y = -30

1) f(x)=-3×4⁽¹⁻ˣ⁾ <--- this can be broken into two segments as seen below 
f(x)=-3x4¹(4⁻ˣ) 
f(x)=-12(4⁻ˣ) 

2) f(x)=log₅(x-2)+log₅(3x+7) <--- since the logs are same, you can add them 
f(x)=log₅((x-2)(3x+7))
f(x)=log₅(3x²+7x-6x-14) 
f(x)=log₅(3x²+x-14) 

I graphed this equation to find the zeros as -2.4 or 2.07. 

3) c⁽⁴ⁿ⁺¹⁾=7a-b 
logc(7a-b)=4n+1 

Hope I helped :)