把口诀和算式填完整
1×7=7          一七得七           7×1=7
2×7=           二七（     ）     7×2=
3×7=           三七（     ）     7×3=
4×7=           四七（     ）     7×4=
5×7=           五七（     ）     7×5=
6×7=           六七（     ）     7×6=
7×7=           七七（     ）     7×7=