D. It is D because x=the number of days times 2 and the 5 you collected
<u><em>Answer:</em></u>
The slope of the line is 77
<u><em>Explanation:</em></u>
We know the speed is constant and that the mile-marker location over time can be represented by a line. This means that the equation is linear.
<u>The slope can, therefore, be calculated as follows:</u>

where (x₁ , y₁) and (x₂ , y₂) are two points on the line
We are given that the two points (1, 123) and (3, 277) are two points in the line
<u>Substitute with them in the above equation to get the slope as follows:</u>

Hope this helps :)
Step-by-step explanation:
y=7x-10
Generally speaking, the number of solutions to an algebraic equation is equal to the exponent of the highest power. so the answer is b.4