As we know the formula to calculate the slope is m = y2 - y1 divided by x2 - x1.
Where m is the slope. y2 is the second y co ordinate. y1 is the first y co ordinate. x2 is the second x co ordinate. x1 is the first x co ordinate.
So to calculate we can write it out as m = 7 - 5 / 9 - 4 which comes out to be 2/5. So the slope of AB is 2/5.