A slope intercept form is, take as an example: y=mx + b, because b is the number where the line intercepts the y axis.
Assuming the space inbetween -7x and 8y is a plus sign.
To get the equation in the right format, one must do the following:
8y=7x-1
y=7/8x-1/8
And theres your answer!
Note: The line intercepts the y axis in -1/8 :)
(If the space isnt a plus, i can answer diffrently in the comments.)