Aline passes through (-1,7)and(2, 10)

Slope
m = (y2-y1)/(x2-x1)
m = (10 - 7)/(2 --1)
m = 3/3
m = 1

To find the equation
y = mx + b
m is slope
y = 1x + b
plug in one of the equations to solve for b
10 = 1(2) + b
10 = 2 + b
subtract 2 from both sides
8 = b

The equation is 
y = 1x + 8
or you can write it as
y = x + 8

Hope this helps