Since subtracting is the same as adding a negative number, the answer is -12 + (-12). Hope this helps!
Answer:
The ball will reach the ground when h=0.
Set the equation equal to 0.

Step-by-step explanation:
The height of a golf ball after it has been hit from the top of a hill can be modeled by the equation
,
where h is the height in feet and t is time in seconds.
When ball will reach the ground the distance between ball and ground is 0. So, the ball will reach the ground when h=0.
To find the time it takes for the ball to reach the ground, set the equation equal to 0 and use the Zero Product Property to solve for $t$.
Solve the equation using the Zero Product Property.
So, 
First, to make things easier, let's turn 5/4 into a decimal given a second is equal to 1000 milliseconds.
5/4 = 1,25
1,25 * 1000 = 1250 milliseconds = 1.25 seconds
So, we've found that 45 yards can be covered in 1.25 seconds. Now we'll use the rule of 3:
45 - 1.25
80 - x
Now we solve:
(80 * 1.25) / 45 = x
100 / 45 = x
2,22... = x
So, according to our answer, 80 yards can be covered in 2,22 seconds, which in fractions would be:

Hope it helped,
BioTeacher101