若3n=2，则33n+2=______．
33n+2=33n•32=（3n）3•9=23×9=8×9=72，
故答案为：72．
—When did he start playing basketball ?
—He began to play ________, and became famous ________. [ ]
A. in the 1990s, in his twenties
B. in 1990, in his twenty
C. in 1990s, in the twenties
D. in the 1990's, in his twenty
怎样去除衣服上的铁锈？
