For this case we have the following system of equations:

We solve by the substitution method:
We substitute the first equation in the second equation:

We apply distributive property considering that 

We subtract 69 from both sides of the equation:

We divide by 8 on both sides of the equation:

We look for the value of the variable y:

Thus, the solution of the system is 
Answer:

Answer:
Answer in file:
Step-by-step explanation:
<h2>
Answer:</h2>
The answer is 16.
<h2>
Step-by-step explanation:</h2>
Since the 8x is positive, the equation must have y as a positive number.
Let's see this!
An easy way to complete the square if you have the constants for x2 and
But not the non-variable number is to divide the x constant, and then square it.
Example:

The last number must be 16. Let's check it.

ABC : DEF
3: 5
3 x 9.6 : 5 x 9.6
28.8 : 48
Perimeter of triangle ABC = 28.8 inch