Let's begin by defining the key terminologies:
The degree of a polynomial simply refers to the term with the highest exponent in a polynomial
For example:

The leading coefficient simply refers to the coefficient of the term that has the highest degree in a polynomial
For example:
Answer:
A
Step-by-step explanation:
area=πr²=π×2²=4π≈4×3.14≈12.56 km²
X + y - 6 = 0
Take out y.
x - 6 = 0
Add 6 to both sides.
x = 6 is your first equation.
x - y - 8 = 0
Take out y.
x - 8 = 0
Add 8 to both sides.
x = 8 is your second equation.
I hope this helps!