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Chris is twice as old as Don, and next year the sum of their ages will be four times as much as Don's age last year. Find their present ages.

Let x=Don's present age

2x=Chris's present age

next year:

x+1=Don's age

2x+1=Chris's age

(x+1) + ((2x+1) = 4 (x-1) (next year the sum of their ages will be four times as much as Don's age last year.)

x+1+2x+1=4x-4

x=6

2x=12

Don's present age=6

Chris's present age=12