45 is the answer i hope this helps
Recall your d = rt, distance = rate * time
so... one train goes west and the goes the opposite way... alrite... so... notice, by the time 338 miles have been covered by both, it will have been "t" hours, and whatever "t" is, is the same amount of time the westbound train has been running as well as the eastbound train has been running.
now, let's say, since by "t" hours they've covered 338 altogether, so, if the westbound train has covered say "d" miles, then the eastbound train would have covered the slack from 338 and d, that is, "338 - d".

so, 2hours and 36 minutes.
Answer:
As shown in picture, this is a trapezoid.
The area of a trapezoid is calculated by:
A = (base1 + base2) x height x (1/2)
To work out A, we need to find out base1, base2, and height.
base1 = YZ = 
base2 = XW =
Otherwise, the height (distance between base1 and base2) is 4 as shown in picture.
=> A = (3 + 7) x 4 x (1/2) = 20
Hope this helps!
:)
With
and
, we have



Then
has critical points where


where
is any integer.
is increasing wherever
, which happens for

