Let x be the age of the house right now.
Given the situation: When the mortgage is completely paid off for Mark and Lynne’s house, it will be 3 times as old as it is now. They have 12 years left on the mortgage.
That means the montage will be completely paid in 12 years.
In 12 years, the age of the house will be x + 12.
Also, in 12 years, the age of the house will be 3 times as old as it is now.
Then, let's equate the age of the house in 12 years:
To find x, subtract x from both sides, then divide both sides by 2:
Answer: The house is now 6 years old.