>(1 - (K11 - L11)/K11) * 100 > = (1 - (K11 / K11) + (L11 / K11)) * 100 Where did the + came from ? (K11 - L11)/K11 is the same as (K11 / K11 ) - (L11 / K11) Besides, the parentheses signifies that it should be evaluated first. the formula is evaluated to; K11 - L11 then divided by K11, subtract the answer from 1 then multiplied by 100 to represent as a percentage. This is a valid income formula. if L11 = 100, K11 = 200, this will result into a 50% answer.