Please solve for me!!

During a trip , Jonathan had driven a total of 75 miles by 6:20 PM and a total of 85 miles by 6:40 Pm. He drove at the same rate for the entire trip. At what time had he driven a total of 140 miles?

8:30 PM

Step-by-step explanation:

Let's say that x is minutes since 6:20 PM, and y is position in miles.

Since Jonathan drives at a constant rate, the position vs time graph is linear.  Two points on the line are (0, 75) and (20, 85).  The slope of the line is:

m = Δy / Δx

m = (85 − 75) / (20 − 0)

m = ½

So the equation of the line is:

y = ½ x + 75

We want to find x when y is 140.

140 = ½ x + 75

65 = ½ x

x = 130

So 130 minutes after 6:20 PM is when Jonathan's position will be 140 miles.  130 minutes is 2 hours and 10 minutes.  So the time will be 8:30 PM.