You can use two method
First method: form a triangle from x = 4 to x = 7. See vertically and horizontally (count the squares). It would be 5 and 3. Therefore 5/3 would be the slope.
Second method: use the slope formula
Determine 2 points on the graph
(4,0) and (7,5)
Formula: (y2-y1)/(x2-x1)
(5-0)/(7-4) = 5/3
The slope is 5/3