First get all the terms on the same side:

Now solve using the quadratic formula which is:

Plug in the values:

So the answer is:
It seems you double the amount each day. keep doing that until you get to 15
Answer:
For any value of x
Step-by-step explanation:
Solve by using system of equations!
3x+12
3(x+4)=3x+12
3x+12=3x+12
x=x
This means that any value of x would create the same answer for both equations.