To find the slope, use the equation of a line:

Plug in the values for x and y:

We know that 2 can fit into 5 twice, which means 2*2 is 4.
We now have
.
If 5 is b more than 4, then this means that 4 is b less than 5. Subtract 4 from both sides, and you will have b = 1.
This means your equation is y = 2x + 1.