(1)计算+4﹣ (2)计算:(2.4﹣)÷﹣×2.3 (3)解方程:5:x=3:6 (4)已知a:b=3:4,b:c=3:5,求a:b:c.
-(+)
0.5×1.6+0.5×26.4
×(+0.8÷)
(+)×(1-)
45÷×-1