part A)
[tex]\bf \begin{array}{ccllll}
hours(x)&velocity(y)\\
-----&-----\\
2&50\\
6&54
\end{array}\\\\
-------------------------------\\\\
\begin{array}{lllll}
&x_1&y_1&x_2&y_2\\
% (a,b)
&({{ 2}}\quad ,&{{ 50}})\quad
% (c,d)
&({{ 6}}\quad ,&{{ 54}})
\end{array}[/tex]
[tex]\bf slope = {{ m}}= \cfrac{rise}{run} \implies
\cfrac{{{ y_2}}-{{ y_1}}}{{{ x_2}}-{{ x_1}}}\implies \cfrac{54-50}{6-2}\implies \cfrac{4}{4}\implies 1
\\\\\\
% point-slope intercept
y-{{ y_1}}={{ m}}(x-{{ x_1}})\implies y-50=1(x-2)\\
\left. \qquad \right. \uparrow\\
\textit{point-slope form}
\\\\\\
y-50=x-2\implies \boxed{y-x=48}\impliedby
\begin{array}{llll}
standard\\
form
\end{array}[/tex]
part B)
well, to graph a LINEar equation, since it's just a LINE, you simply need two points to graph a line, and since we know that y - x = 48.... if you want to know what's "y" when x = 7? or 7 hours, well
y - (7) = 48
y = 48 + 7
y = 55
so.. that's the point for the 7th hour, 7, 55, and you can pick any other point above, and graph it away.