Atrain left podunk and traveled west at 70 km/hr. two hours later, another train left podunk and traveled east at 90 km/hr. how many hours had the first train traveled when they were 1420 km apart

The first train going west traveled by 7 hours and 45 minutes  

Step-by-step explanation:

Given as :

The speed of west going train = 70 kmph

The speed of east going train  = 90 kmph

Distance between both the train is 1420 km

Let the distance cover by east going train = x km

So, The distance cover by west going train = (1420 - x) km

The west going train travel for T hour

And The east going train travel for ( T + 2 ) hour

Now, From Distance = speed × time

For east going train

x = 90 × ( T + 2 )

Or, x = 90 T + 180  

For west going train

1420 - x = 70 × T

So, from above equations :

1420 - (90 T + 180 ) = 70 T

Or, 1420 - 180 = 70 T + 90 T

Or, 1240    =  160 T

∴  T =

So, T = 7.75 hours

Or,  T = ( 7 + ) hours

Or,  T = (7 + ) hours

Or, T = 7 hours and 45 minutes

Hence The first train going west traveled by 7 hours and 45 minutes   Answer

yes because there is exactly one y value for every x value

for function there can't be more than one value for every x value