Question 1062225
he makes 10 durians for 30 dollars.


he sells each durian for 7 dollars.


let x = the number of durians he sells.


his revenue is 7 * x.


his cost is 30.


his revenue must be greater than his cost to make a profit, so you get:


7 * x >= 30


solve for x, and you get x >= 30/7 which becomes x >= 4 and 2/7.


since he can't sell part of a durian, than x >= 5 is the answer.


when he sells 4 durians, he makes 28 dollars.


when he sells 5 durians, he makes 35 dollars.


he starts making a profit when he sells at least 5 durians.