ok... so week #4 he earned $100 approximately. this is so because in the four weeks of working, he made in total, $400. so 400/4 = 100.
For weeks #s 5 and 6, he made a total of $1,000 because he made 500 for week 5 and 500 for week six ( the last 2 weeks)...
So all in all, he made $1,100 in the last 3 weeks...
Do you get it?