The slope-point formula:
[tex]y-y_1=m(x-x_1)\\\\m=\dfrac{y_2-y_1}{x_2-x_1}[/tex]
We have:
[tex](-1,\ 1.5)\to x_1=-1,\ y_1=1.5\\(0.5,\ 0.5)\to x_2=0.5,\ y_2=0.5[/tex]
Substitute:
[tex]m=\dfrac{0.5-1.5}{0.5-(-1)}=\dfrac{-1}{1.5}=-\dfrac{1}{\frac{3}{2}}=-\dfrac{2}{3}\\\\y-1.5=-\dfrac{2}{3}(x-(-1))\\\\y-1.5=-\dfrac{2}{3}x-\dfrac{2}{3}\\\\y-\dfrac{3}{2}=-\dfrac{2}{3}x-\dfrac{2}{3}\ \ \ |+\dfrac{3}{2}\\\\y=-\dfrac{2}{3}x-\dfrac{2}{3}+\dfrac{3}{2}\\\\y=-\dfrac{2}{3}x-\dfrac{2\cdot2}{3\cdot2}+\dfrac{3\cdot3}{2\cdot3}\\\\y=-\dfrac{2}{3}x-\dfrac{4}{6}+\dfrac{9}{6}\\\\y=-\dfrac{2}{3}x+\dfrac{5}{6}[/tex]
