Fred saves half as much as john. john saved four times as much as mary. together all three save $280 dollars. how much did each person save

How do you use the elimination method for this question? explain, because i really want to understand!

Use the given degree of confidence and sample data to construct a confidence interval for the population mean mu . assume that the population has a normal distribution. a laboratory tested twelve chicken eggs and found that the mean amount of cholesterol was 185 milligrams with sequals 17.6 milligrams. a confidence interval of 173.8 mgless than muless than 196.2 mg is constructed for the true mean cholesterol content of all such eggs. it was assumed that the population has a normal distribution. what confidence level does this interval represent?

What is the equation of the parabola with focus (-1,-1) and directrix y=1?