He earns 1800 so, 3000 minus 1800 is 1200, if u set this up as a proportional relationship you'll get 1200 = 3 x 100
cross multiply the relationship, 1200 by 100 is 120,000, 3 by x is 3x, 3x=120,000 isolate the variable so you divide 3x by 3 and get 1x, what you do to one side you have to do to the other so 120,000 divide by 3 is 40,000. If max wants to earn at least 3000 this month he will have to sell at least 40,000 dollars in items
