f + 1/4 = 2/3
You start by subtracting 1/4 from both sides of the equation
Then you now have
f = 2/3 - 1/4
Take the LCM as 12 (Least common multiple of 3 and 4)
f = (4[2] - 3[1]) / 12
f = (8 - 3) / 12
f = 5/12
