Answer:
Mary is 10 years old
Explanation:
John age is twice Mary age
Let John's age = 2y
Mary's age = y
Five years ago
John's age = 2y - 5
Mary's age = y - 5
John age was three times Mary age
John's age = 3(y - 5)
Mary's age= y -5
Equate John's age Five years ago to John's age Three times
i.e. John's age Five years ago = John's age Three times Mary
2y - 5 = 3 (y - 5)
2y - 5 = 3y - 15
-5 + 15 = 3y - 2y
10 = y
y = 10
Hence, Mary's age now is 10 years