Respuesta :
you can use point-slope form
y-y1=m(x-x1)+b
y-12=0.5(x-(-9))+3
y-12=0.5(x+9)+3
y=0.5x+4.5+3+12
y=0.5x+19.5
y-y1=m(x-x1)+b
y-12=0.5(x-(-9))+3
y-12=0.5(x+9)+3
y=0.5x+4.5+3+12
y=0.5x+19.5