The number of bacteria in a culture is increasing according to the law of exponential growth. There are 125 bacteria in the culture after 2 hours and 350 bacteria after 4 hours.
First, the dot stands for the "product". You have to multiply.
5/8* 2/7
= [5/ (2*4)]* (2/7)
= 5/4* 1/7 (because 2 and 2 cancel out)
= (5*1)/ (4*7)
= 5/28
The final answer is 5/28~
I'm not sure if this is the easiest way of doing this, but it surely work.
Let the base of the triangle be AB, and let CH be the height. Just for reference, we have

Moreover, let CH=y and BC=z
Now, AHC, CHB and ABC are all right triangles. If we write the pythagorean theorem for each of them, we have the following system

If we solve the first two equations for y squared, we have

And we can deduce

So that the third equation becomes

(we can't accept the negative root because negative lengths make no sense)
I used the cross product method
5x = 2.4 •3
5x=7.2
7.2divided by 5
1.44 miles in 3 hours
Hope I helped