Answer:
B) 5 hours
Step-by-step explanation:
First, find the amount of mph between 60 and 80:
80 - 60
= 20 mph
Since the speed increases 4 mph per hour, we can find how long it will take to get to 80 mph by dividing 20 by 4:
20/4
= 5
So, the correct answer is B, 5 hours
The answer is the first one, A
<h2>
Answer:</h2>

<h2>
Step-by-step explanation:</h2>
We will use the Gaussian elimination method to solve this problem. To do so, let's follow the following steps:
Step 1: Let's multiply first equation by −2. Next, add the result to the second equation. So:

Step 2: Let's multiply first equation by −1. Next, add the result to the third equation. Thus:

Step 3: Let's multiply second equation by −35, Next, add the result to the third equation. Therefore:

Step 4: solve for z, then for y, then for x:


By substituting
into the first equation, we get the
. So:
