两条直线相交就一定是垂直. .
填空 (1)0.8= %=== ÷10= : . (2)=14÷ = %= : = (小数)
5:13==1.2: .
9÷ =0.6= :20=30: .
= :15==6÷ = (填小数)
:8=15÷ ==9: .