Answer:
20
Step-by-step explanation:
The time when the two trains reach each other is 1.25 hours
The trains are 68.75 away from the city when they reach each other.
The new mean age will be greater than 14.2 years because the teacher is older than the previous mean.
Find common factor, in this case the common factor is 10x
So the answer would be 10x(x^6 - y^10)