Given x and y are rational numbers, when is |x+y|=|x|+|y| true?

If olu is twice as old as funmi if the sum of their ages is 60 how old is olu

Abicycle training wheel has a radius of 3 inches. the bicycle wheel has a radius of 10 inches.approximately how much smaller, in square inches and rounded to the nearest hundredth, is the area of the training wheel than the area of the regular wheel? *

Is experimental probibilty the same as the observed frequency in math? i need the answer asap!