There isn't any. " yx-1 " is not an equation.
Because you did not supply the image, we cannot see the symbols. It is therefore impossible to give a proper answer to your question. Please resubmit your question spelling out the symbols as "plus", "minus", "times", "equals". The question is about "yx" which is not a mapping and so does not have a slope.
Slope for the equation y equals 7 is zero.
The slope is 4.4 and the y intercept is -7
If: y = 7 then there is no slope and the line will be parallel to the x axis
The slope of the line of 2x plus 2y equals 7 is (7/2x - 1).
Slope = -1
4x+y = 7 y = -4x+7 in slope-intercept form So the slope is -4