Find the linear approximation of the data that passes through the points (5, 3) and (20, 6).

Y = mx + b
m = (y₂ - y₁)/(x₂ - x₁)
m= (6-3)/(20-5) and m = 3/15 = 1/5. Now calculate b.
To that end plug any of the 2 pairs value, let's take (5,3)
y = (1/5).x + b
3 = (1/5).(5) + b & b= 2

The equation: (1/5)x + 2