Explanation:
a general line equation is
y = ax + b
"a" being the slope is the line, "b" being the y-intercept (the y value when x = 0).
we see from the 2 marked points (by we could choose any points on the line) that
y changes by 2 units, when x changes by 3 units.
so the slope is 2/3.
we use one point (1, 2) to solve for b
2 = 2/3 × 1 + b = 2/3 + b
6/3 = 2/3 + b
4/3 = b
and the full equation is
y = 2/3 x + 4/3