When Truck A travels at a constant speed of m miles per hour for 84 mi

Distance by Truck A = m * 84/60
Distance by Minivan B = n * 252/60

So 7(m/5) - 21(n/5) = 14

=> m - 3n =10

Hence m can be 64, n can be 18.

Truck A travels at m mph for 84 minutes => distance covered by Truck A= \frac{m*84}{60}
Similarly Minivan B travels at n mph for 252 minutes => distance travelled by B = \frac{n*252}{60}

As per the question Truck A travels 14 miles more than B:
\frac{m*84}{60}-\frac{n*252}{60}=14
Simplifying the equation we will get
m-3*n=10

From the options if we take m=64 and n=18 => then only m-3*n=10 equation is satisfied.

Dist A- Dist B=14
84m/60-252n/60=14
-21n+7m=70
-3n+m=10----> m>n
Thus by testing answer choices , we get m=64 and n=18

Question: In the first column, select the row that corresponds to the value of m, and in the second column select the row that corresponds to the value of n.

Given: When Truck A travels at a constant speed of m miles per hour for 84 minutes,
This can be translated as Distance travelled by A = m * (84/60)

Minivan B travels at a constant speed of n miles per hour for 252 minutes
This can be translated as Distance travelled by B = n * (252/60)

Truck A travels 14 miles more than minivan B.
This can be translated as (m * (84/60)) - (n * (252/60)) = 14
Simplifying this further we get - m = 10 + 3n

Now let's assume the value of n = 12 then m = 46. 46 is not one of the options hence n is not equal to 12.

Now let's assume the value of n = 18 then m = 64. 64 is one of the options hence n can be equal to 18.
We can stop here and mark these as the answers.
We can also see that the next value of n could be 36 and the corresponding m value will be 118 which is not an option. And as value of n keeps increasing the value of m will also keep increasing. Hence, not other choice is sufficient.

Hence m = 64 and n = 18.

in 84 minutes A travel 7m/5 miles and in 252 minutes B travels 21n/5 miles. There difference is given as 14 miles.
7m-21n=70 solve it .we get m=64 and n=18

When Truck A travels at a constant speed of m miles per hour for 84 minutes, and Minivan B travels at a constant speed of n miles per hour for 252 minutes, Truck A travels 14 miles more than minivan B.

In the table, select values of m and n that are consistent with the information given. In the first column, select the row that corresponds to the value of m, and in the second column select the row that corresponds to the value of n. Select only one option in each column.

Keeping values for Speed ie, m and n in km/h , we get the equation as

m (84/60) - n(252/60) = 14

7m - 21n = 70

m = 3n + 10 ..................(1)

Only m= 64, n = 18 satisfy Equation (1)

Value of m = 64
Value of n = 18