First, solve the equation for y.
-7x - 2y = 56 Add 7x to both sides
-2y = 56 + 7x Divide both sides by -2
y = -28 - 4.5x Switch the two terms to match slope-intercept form
y = -4.5x - 28
In slope-intercept form (y = mx + b), the m is slope and b is the y=intercept. In this case, m = -4.5, so your slope is -4.5 or
.