0.7777×0.7＋0.1111×5.1
=0.1111×7×0.7＋0.1111×5.1
=0.1111×(7×0.7)＋0.1111×5.1
=0.1111×(7×0.7+5.1)
=0.1111×(4.9+5.1)
=0.1111*10
=1.111