The point slope formula is
y-y1=m(x-x1)
M represents slope and (y1, x1) are the coordinates to your point.
From this question we know the slope is -1/7 so you plug that in to the formula which will give you
Y-y1=-1/7(x-x1)
There isn’t a point attached to this question so let’s make up a point and say it’s (1,7). You plug this into the equation to get
Y-7=-1/7(x-1)
This is your equation.