SOLUTION: 1. The sum of the ages of John and Jacob is 20 years. Two years from now , one will be thrice as old as the other then. Find their present ages. 2. The sum of the ages of Manny an

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Question 139492This question is from textbook
: 1. The sum of the ages of John and Jacob is 20 years. Two years from now , one will be thrice as old as the other then. Find their present ages.
2. The sum of the ages of Manny and Dennis is 47 years. Seven years ago, Manny was twice as old as Dennis was then. How old is each now? This question is from textbook

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
1. The sum of the ages of John and Jacob is 20 years. Two years from now , one will be thrice as old as the other then. Find their present ages.
:
Jo + Ja = 20
Jo = (20 - Ja); use for substitution
:
Write an equation for the statement:
"Two years from now , one will be thrice as old as the other then."
Jo + 2 = 3(Ja + 2)
Jo + 2 = 3Ja + 6
Jo = 3Ja + 6 - 2
Jo = 3Ja + 4
Substitute (20-Ja) for Jo
20 - Ja = 3Ja + 4
20 - 4 = 3Ja + Ja
16 = 4Ja
Ja = 16%2F4
Ja = 4 yrs
:
Jo = 20 - 4 = 16 yrs old
:
:
2. The sum of the ages of Manny and Dennis is 47 years.
M + D = 47
M = 47 - D
;
Seven years ago, Manny was twice as old as Dennis was then.
M - 7 = 2(D-7)
:
How old is each now?
Solve this one the same way as we did the 1st one.