4 only has three factors 1,2,4. 4 times 1 and 2 times . No other possible combinations making Adam wrong.
Let the slower train's velocity be x-21
Let the faster train's velocity be x
We know that the approach speed is the sum of both speeds, so x+x -21= 2x-21.
The approach rate is given by Distance/time = 471/3 = 157mpH
x+x-21=157
2x=157+21
2x=178
x=89mph
The slower train is travelling 89-21 = 68mph
The faster train is travelling 89mph.
Given:
Consider the given gallons are 
gallons.
To find:
The number of quarts in gallons.
Solution:
We know that,
1 gallons = 4 quarts
Using this conversion, we get
Therefore, there are 33 quarts in gallons.
I feel it should be 30 because x represents the number of lessons, and 30 is multiplied by that.
