Đáp án:
Giải thích các bước giải:
`1.`
`a)\ 3/5=(3×5)/(5×5)=15/25`
`b)\ 7/9=(7×6)/(9×6)=42/54`
`c)\ 3/4=(3×2)/(4×2)=6/8=(6×5)/(8×5)=30/40=(30:2)/(40:2)=15/20=21/?` (đề sai)
`d)\ 48/64=(48:8)/(64:8)=6/8`
`e)\ 121/88=(121:11)/(88:11)=11/8`
`f)\ 20/25=(20:5)/(25:5)=4/5=(4×7)/(5×7)=28/35=?/45` (đề sai)
`2.`
`a)\ 225:25=(225:5):(25:5)=45:5=9`
`b)\ 60:15=(60:5):(15:5)=12:3=4`