What is the slope of the line in this graph

The slope is

                   (change in 'y') divided by (change in 'x')

between any two points.

The graph starts at the origin.  That's the point (0, 0). 
We just need one more point.

It looks to me like the graph exactly goes through the point (7, 5).

So there you have it.
From the point (0, 0) to the point (7, 5),
the change in 'y' is 5 and the change in 'x' is 7 .
To calculate the slope, use the formula I gave you up at the top.