Let’s call the speed of the slower car S, then the speed of the other is S+10mph.
At 5pm they have been travelling for 3 hours. The slower car travels a distance 3S and the faster one 3(S+10).
But the two distances must add up to 240 miles so 3S+3(S+10)=240, 3S+3S+30=240, 6S=210, S=35 mph. The faster car’s speed is 45mph. We can see that 3S is the same distance as 3x, so x=S=35 mph, and the distance the faster car travels is 3×45=135 miles.
You find the slope of the line by using the formula 
where x1 and y1 is the first point, and x2 and y2 are the second point.
What are you looking for? The X? Tell us exactly.
Find the x and y intercepts or any other 2 points. (I advise you finding the y intercept though.)
then calculate for slope using:
y(2) - y(1)
________
x(2) - x(1)
The (2) and (1) are not exponents they are small numbers at the bottom of the numbers.
The slope is: 4
