First, find the slope:
slope = (y2 - y1) / (x2 - x1)
slope = (1/4 - 1/3) / (3/4 - 1/2)
slope = (3/12 - 4/12) / (3/4 - 2/4)
slope = (-1/12) / (1/4)
slope = (-1/12) * (4/1)
slope = -1/3
.
Now we do point-slope form:
y - y1 = m(x - x1)
y - 1/3 = (-1/3)(x - 1/2)
y - 1/3 = (-1/3)x + 1/6
y = (-1/3)x + 1/6 + 1/3
y = (-1/3)x + 1/6 + 2/6
y = (-1/3)x + 3/6
y = (-1/3)x + 1/2