Question 369484
the sum of william's age and fred's age is 20 years. William's age 1 year from now will be 9 times fred's age 1 year ago. Find the present age of each

Let W = the present age of William
    F = the present age of Fred

1st equation
W+F = 20
  W = 20 - F

2nd equation
W + 1= 9(F-1)
since W = 20-F in 1st equation 
The 2nd equation becomes
(20-F) + 1 = 9(F-1)
20-F + 1 = 9F - 9
      10F= 30
        F = 3

        W = 20 - 3
          = 17