Let
x--------> the time in hours
y-------> the distance in miles
we know that
The speed is equal to

in this problem


<u>Equation First Train</u>

<u>Equation Second Train</u>

---------> equation 
Substitute the values of
and
in the equation 

Solve for x


therefore
<u>the answer is</u>

8x -2y + x+x
simply combine like terms
8x+ x + x= 10x
therefore
10x-2y is equivalent

So, Option C is the correct answer.
Hope this will help you.
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The area of the rectangular roof shingle is 70 inches