Question 479604
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