To complete the sentence, you can express the relationship between David's weight and his nephew's weight in terms of a ratio. Since David weighs 147.6 pounds and his nephew weighs 14.76 pounds, you could choose to express it as follows:
David weighs 10 times (or 10X) his nephew’s weight, since:
\[ 147.6 \div 14.76 = 10 \]
Thus, the completed sentence could be:
David weighs 10 times as much as his nephew weighs.