[tex]\bf \begin{array}{ccll}
\stackrel{x}{days}&\stackrel{y}{toys}\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
3&4\\
9&10
\end{array}\\\\
-------------------------------\\\\
\begin{array}{ccccccccc}
&&x_1&&y_1&&x_2&&y_2\\
% (a,b)
&&(~ 3 &,& 4~)
% (c,d)
&&(~ 9 &,& 10~)
\end{array}[/tex]
[tex]\bf slope = m\implies
\cfrac{\stackrel{rise}{ y_2- y_1}}{\stackrel{run}{ x_2- x_1}}\implies \cfrac{10-4}{9-3}\implies \cfrac{6}{6}\implies 1
\\\\\\
% point-slope intercept
\stackrel{\textit{point-slope form}}{y- y_1= m(x- x_1)}\implies y-4=1(x-3)
\\\\\\
y-4=x-3\implies y=x+1[/tex]
