Question 139492
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 = {{{16/4}}}
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.