2×9+3=____
6×5+2=____
Mrs. Black teaches us Chinese. (对划线部分提问.)
____
已知向量a=4,3,b=-1,2,若向量a+kb与a-b垂直,则k的值为( )
— Let's go now . But where is Eric ?
— Oh, he can't go with us . He ___ some foreigners around our company