Answer:
in logarithm + works as a * for numbers with the same bases.
Step-by-step explanation:
Three million five hundred thousand or three and a half million


keep in mind, that "t" is the time when the train at A station, left towards B station
they met, at some time "t", and by the time that happened, train from A
which started 3 hours earlier, had already covered "d" distance,
whatever that is
and the train coming from B, covered, 600-d, or the difference
X-6=36
x=42
Hope that helps