Question 931198
1. Dave is four times as old as Rob. Five years ago, Rob 
was 30 years younger than Dave. Find their present 
ages.
D = 4R
R = D-30
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Substitute::
R = 4R-30
-3R = -30
Rob = 10 yrs
D = 4R = 40 yrs
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 2.Tom is 8 years older than Alex. 3 years ago, Alex was 
2 years more than one-third as Tom was then.How old is tom.
T = A + 8
A-3 = (1/3)(T-3)+2
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Substitute::
T-8-3 = (1/3)T - 1 + 2
T-11 = (1/3)T + 1
(2/3)T = 2
T = 3 yrs
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 3.John is twice as old as his wife Mary. Five years 
ago,John was 10 years younger than 3 times Mary's
 age. How old is Mary now?
J = 2M
J-5 = 3(M-5)-10
2M-5 = 3M-25
M = 20 yrs
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Cheers,
Stan H.
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