65 = 12.1+h the flower is 65 inches. it has grown 12.1 inches since the last time he measured it. the last time he measured it, it was height h.
65 = 12.1 + h
subtract 12.1 from both sides
65-12.1 = 12.1 + h- 12.1
52.9 = h
The last time he measured it it was 52.9 inches