Question

括号1/30+1/35+1/63括号乘以二又1/7等于多少？

Answer 1

(1/30+1/35+1/63)×2又1/7
={1/30+1/2[(1/5-1/7)+(1/7-1/9)]}×15/7
=[1/30+1/2×(1/5-1/9)]×15/7
=(1/30+1/2×4/45)×15/7
=(3/90+4/90)×15/7
=7/90×15/7
=1/6

Answer 2

这个就是：
（1/30+1/35+1/63）x15/7
=1/30x15/7+1/35x15/7+1/63x15/7
=1/14+3/49+5/147
=21/294+18/294+10/294
=49/294
=1/6

Answer 3

（1/30+1/35+1/63）×15/7
=1/30×15/7+1/35×15/7+1/63×15/7
=1/14+1/14+5/147
=2/7+5/147
=42/147+5/147
=47/147