y = mx + b

where m is the slope and b is the y -intercept.

The x-intercept is the point at which y equals 0. So, set y equal to 0 in the general formula:

0 = mx + b

x = -b/m

The y-intercept is when x = 0 and is equal to b, as said above.

For the rest of it:

sum = 60 = -b/m + b

difference = 60 = -b/m – b

What I’d do at this point is add the two equations.

120 = -b/m + (-b/m) + b – b

120 = -2b/m

-60 = b/m

From there, you can choose any numbers you want that make this expression equal to -60. For example, b = 60 and m = -1 would give you the equation y = -x + 60. Or, b = -30 and m = 0.5 gives you y = 0.5x – 30.