题目

Buck lived in Mr. Miller’s big house in the sunny Santa Clara valley. There were large gardens and fields of fruit trees around the house, and a river nearby. In a big place like this, of course, there were many dogs. There were house dogs and farm dogs, but they were not important. Buck was chief dog; he was born here, and this was his place. He was four years old and weighed sixty kilos. He went swimming with Mr. Miller’s sons, and walking with his daughters. He carried the grandchildren on his back, and he sat at Mr. Miller’s feet in front of the fire in winter.   But this was49.56-6.8-3.2=49.56-（ + ）