So first you are going to want to find the slope of the equation. The equation for that it (y2 - y1)/(x2 - x1) = (10 - 7)/(2 - -1) and that equals 1. So your slope will be 1.
Now you have half of your equation complete, currently it looks like, y = x + b. So we have to find the y intercept. You can do that by plugging in a pair of coordinates into the current equation and solve for b.
Lets plug in (2,10)
10 = 2 + b
10 - 2 = b
b = 8
So now you have your equation in slope intercept form, y = x + 8. Just move the x over to the left side and there is your answer.
