Answer: 67 years and 134 years
In this case, you are given the buildings sum ages ( building A ages+ building B ages = 201 years) and the building ratio ( Building A ages= 2x Building B ages).
To answer the question, you simply need to insert the second equation into the first. It would be:
building A ages + building B ages= 201
2x building B ages + building B ages= 201
building B ages= 67 years.
Then building A ages= 2x 67 years= 134 years.