There are 4 reds out of 10 so the probability for a red would be 4/10 and for a yellow it would be 1/10. multiply them together to get 4/100 so your probability would be 1/25 or 0.04 or 4%
200-50= 150 So you need to get 150 dollars in a month. If you get 20 dollars a week, then 150/20 will give you 7.5. So it will take you 7.5 weeks to get 150 dollars