SOLUTION: Seven years ago, Mary was six times as old as Cora. In one year, she will only be twice as old as Cora. Find their present ages.

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Question 479604: Seven years ago, Mary was six times as old as Cora. In one year, she will only be twice as old as Cora. Find their present ages.
Answer by Maths68(1474) About Me  (Show Source):
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Mary’s age = M
Cora’s age = C
Seven year ago means we have to subtract 7 from Mary and Cora’s age
M-7=6(C-7)
M-7=6C-42
M=6C-42+7
M=6C-35……………..(1)
In one year means we have to add one years in Mary and Cora’s age
M+1=2(C+1)
M+1=2C+2
M=2C+2-1
M=2C+1………….(2)
Subtract (2) from (1)
M=6C-35
-M=-2C-1
------------
0=4C-36
4C=36
C=36/4
C=9
Put the value of C in equation (1)
M=6C-35
M=6(9)-35
M=54-35
M=19
Mary is 19 years old
Cora is 9 years old