\(B1\\ a,=\dfrac{5.2}{6.4}=\dfrac{5}{12}\\ b,=\dfrac{27}{49}.\dfrac{7}{3}=\dfrac{27.7}{49.3}=\dfrac{9}{7}\\ c,=\dfrac{4}{5}.\dfrac{8}{15}=\dfrac{4.8}{5.15}=\dfrac{32}{75}\\ d,=\dfrac{49}{51}.\dfrac{17}{7}=\dfrac{49.17}{51.7}=\dfrac{7}{3}\)
\(B2\\ =\dfrac{9.3+1.4}{12}-\dfrac{2}{5}=\dfrac{31}{12}-\dfrac{2}{5}=\dfrac{31.5-12.2}{60}=\dfrac{131}{60}\\ b,=\dfrac{2.4+3.3}{12}-\dfrac{4}{5}=\dfrac{17}{12}-\dfrac{4}{5}=\dfrac{17.5-12.4}{60}=\dfrac{37}{60}\)
`5/6 xx 2/4=5/6 xx 1/2 = (5xx1)/(6xx2) = 5/12`
`27/49 : 3/7 = 27/49 xx 7/3 = (27 xx 7)/(49 xx 3)= ( 9 xx 1)/(7 xx 1) = 9/7`
`4/5 : 15/8 = 4/5 xx 8/15 = (4xx8)/(5xx15) = 32/75`
`49/51 : 7/17 = 49/51 xx 17/7 = (49 xx 17)/(51 xx 7)= ( 7 xx 1)/(3 xx1) = 7/3`
`9/4 + 1/3 - 2/5 = 135/60 + 10/60 - 24/60 =(135 + 20 - 24)/60 = 131/60`
`2/3 + 3/4 - 4/5 = 40/60 + 45/60 - 48/60 = (40+45-48)/60 = 37/60`
