a:=91/105+60/105-101/105=50/105=20/21
b: =2/5+8/27=54/135+40/135=94/135
c: =15/8x7/6=105/48=35/16
\(\dfrac{13}{15}+\dfrac{4}{7}-\dfrac{101}{105}=\dfrac{91}{105}+\dfrac{60}{105}-\dfrac{101}{105}=\dfrac{50}{105}=\dfrac{10}{21}\)
\(\dfrac{2}{5}+\dfrac{2}{3}\times\dfrac{4}{9}=\dfrac{2}{5}+\dfrac{8}{27}=\dfrac{94}{135}\)
\(\dfrac{3}{4}\times\dfrac{5}{2}\times\dfrac{7}{6}=\dfrac{105}{48}=\dfrac{35}{16}\)
\(a,=\dfrac{13.7+4.15-101}{15.7}=\dfrac{91+60-101}{105}=\dfrac{50}{105}=\dfrac{10}{21}\\ b,=\dfrac{2}{5}+\dfrac{2.4}{3.9}=\dfrac{2}{5}+\dfrac{8}{27}=\dfrac{2.27+8.5}{135}=\dfrac{94}{135}\\ c,=\dfrac{3.5}{4.2}.\dfrac{7}{6}=\dfrac{15}{8}.\dfrac{7}{6}=\dfrac{15.7}{8.6}=\dfrac{105}{48}=\dfrac{35}{16}\)
`13/15 + 4/7 - 101/105= 91/105 + 60/105 - 101/105 = (91+60-101)/105 = 50/105 =10/21`
` 2/5 + 2/3 xx 4/9`
`=2/5 + (2xx4)/(3xx9)`
`=2/5 + 8/27`
`=14/135 + 40/135`
`=(14+40)/135`
`=54/135`
`=2/5`
`3/4 xx 5/2 xx 7/6`
`=(3xx5xx7)/(4xx2xx6)`
`=105/48`
`=35/16`
13/15+4/7-101/105
=13×7/15×7 + 4×15/7×15 - 101/105
=91/105 + 60/105 - 101/105
=50/105
2/5+2/3×4/9
=2/5 + 2×3/4×9
=2/5 + 6/36
=2×7,2/36 + 6/36
=20,4/36
3/4×5/2×7/6
=3×5×7/4×3×6
=105/72
