SOLUTION: The ratio of the present ages of Kwasi and Yaw is 2:9. Four years ago the sum of their ages was 47. How old is Yaw now

Let Y be the Yaw age.


Then from the condition, Kwasi's age is  (47 + 4 + 4 - Y) = 55 - Y.


From the condition, you have this proportion


     = .


Hence,

    9*(55 - Y) = 2Y

    9*55- 9Y = 2Y

    9*55 = 2Y + 9Y = 11Y.


Hence,  Y =  = 9*5 = 45 is the Yaw's age now.