SOLUTION: Eighteen years ago the ratio of As age to B s age was 8:13. Their present ratios are 5:7. What is the present age of A?

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Question 1007748: Eighteen years ago the ratio of As age to B s age was 8:13. Their present ratios are 5:7. What is the present age of A?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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Eighteen years ago the ratio of As age to B s age was 8:13.
Their present ratios are 5:7. What is the present age of A?
:
let x = the multiplier
then
5x = A's present age
and
7x = B's present age
:
18 years ago:
%28%285x-18%29%29%2F%28%287x-18%29%29 = 8%2F13
cross multiply
13(5x-18) = 8(7x-18)
65x - 234 = 56x - 144
65x - 56x = -144 + 234
9x = 90
x = 90/9
x = 10 is the multiplier
then
A = 5(10)
A = 50 yrs old now
:
:
Confirm this solution, find B's age; 10*7 = 70yrs old
%28%2850-18%29%29%2F%28%2870-18%29%29 = 32%2F52 = 8%2F13