Answer:
I is at least ten because of nine it rounds to ten
D. Warm air rises and cool air sinks
Answer:
- The two solutions are:

- The next and every step are below.
Explanation:
1.
: Given (addition property / add - 3 to both sides)
2.
: Given (commom factor - 2)
3. 
To obtain the perfect square it was added the square of half of the coefficient of x: (1/2)² = 1/4, inside the parenthesis.
Since, the terms inside the parentthesis are multiplied by - 2, you have to add - 2 (1/4) = - 1/2 to the left side of the equation.
4. Now, you have that the trinomial x² - x + 1/4 is a square perfect trinomial which is factored as (x - 1/2)² and get the expression:

5. Divide both sides by - 2 to get the next expression:

6. The last step is to extract squere root from both sides of the equality:

10x^2 - y + 12 - 3x^2
10x^2 - 3x^2
When you see a number that look almost the same you add or subtract
10x^2 - 3x^2
Always carry the symbol in front of the number