Hi syiro,

First you have to thoroughly read through and understand the material, so first you have to find the 3 equation.

first paragraph (in english) u gotta find the equation for the total number of houses sold of each kind equals to the capital

1: 3A+5B+6C=630

on the 2nd line of the 2nd paragraph (in english)

2: A+B+C=140

thrid paragraph, here it says the profit, so in order to get the profit of each house, you gotta take the selling price of each house minus off the construction costs so,

3:A(5.5-3) + B(9-3) + C(11-6) = 515

A+B+C=140

3A+5B+6C=630

A(5.5-3) + B(9-3) + C(11-6) = 515

so from these 3 equation, Im pretty sure you know how to do from that on, try it out

Good Luck with that. Hope that helps.