爷爷的年龄是爸爸的2倍,爸爸的年龄是儿子的7倍,已知爷爷的年龄是70岁,儿子的年龄是几岁?
直接写出得数.×= 1÷= ×= 77:63=÷9= ×= ÷8= 4:2.5=×=
×= 0×= ÷= = = =
直接写出得数×3= ×16= ×= (+)×4=×+×= += ÷3= 4÷=
= = = == = = == = = == = = =
×1= 52﹣42= 0.75﹣0.5= ×= ÷= 125×0.08=0.5+0.02= ÷= ÷= 0.15×6= 12÷0.3= 0÷=