Question 240499
Hint: the slope formula is {{{m=(y[2]-y[1])/(x[2]-x[1])}}}. So plug in the given coordinates and the slope to get {{{0=(r--5)/(6-7)}}} and simplify to get {{{(r+5)/(1)=0}}}. Now solve for 'r' to get {{{r+5=0}}} --> {{{r=-5}}}



So the second y coordinate is -5. It turns out that to have a slope of zero, the y coordinates must be the same.