`#Mon`
`@\text{ Rút gọn:}`
`\frac{12}{16}=\frac{12:4}{16:4}=\frac{3}{4}`
`\frac{24}{21}=\frac{24:3}{21:3}=\frac{8}{7}`
`\frac{5}{20}=\frac{5:5}{20:5}=\frac{1}{4}`
`\frac{7}{49}=\frac{7:7}{49:7}=\frac{1}{7}`
`@\text{ Tính phân số cùng mẫu:}`
`+)\frac{12}{16}+\frac{5}{20}`
`=\frac{3}{4}+\frac{1}{4}`
`=\frac{4}{4}=1`
`+)\frac{24}{21}-\frac{7}{49}`
`=\frac{8}{7}-\frac{1}{7}`
`=\frac{7}{7}=1`
`=>\frac{12}{16}+\frac{5}{20}+\frac{24}{21}-\frac{7}{49}`
`=1+1`
`=2`
`=>\text{ Chọn C}`
