Let x be the length of the train.
On the basis of the observer;
Speed of the train = x/6
On the basis of the bridge;
Total distance covered by any point of the train= 350+x
Speed = (350+x)/20
Equating the two expressions of speed;
x/6 = (350+x)/20
20(x) = 6(350+x)
20x = 2100+6x
(20-6)x = 2100
14x = 2100
x= 2100/14 = 150 m
Speed = x/6 = (350+x)/20 = 150/6 = 500/20 = 25 m/s.
Therefore,
Length of train = 150 m
Speed of train = 25 m/s
Answer:
D. 
Step-by-step explanation:
If you use Desmos and enter (-3,-1) then enter your lines you can match them up.
This can also be written as A = s^2 and the area would be 49 with a side length of 7.
In order to find this, you can stick 7 into the area equation.
A = s^2
A = 7^2
A = 49
