2 - x = 1/5 : 1/4

2 - x = 1/5 * 4

2 - x = 4/5

x = 2 - 4/5

x = 6/5

3 - x = 1/3 : 1/6

3 - x = 1/3 * 6

3 - x = 2

x = 3 - 2

x = 1

b) 1/3 * 1/2 + 1/5 * 1/2

= 1/2 * (1/3 + 1/5)

= 1/2 * 8/15

= 4/15

373737/414141 : 4545/4141

= 37/41 : 45/41

= 37/41 * 41/45

= 37/45

2727/4242 + 13/42 + 444444/424242

= 9/14 + 13/42 + 22/21

= 2

hoa mắt quá, mk đang tính

kết quả = 1/13 đúng ko bn, k mk nha ( nếu đúng )

a) 1313/2121 . 165165/143143 . 424242/151515

= 13/21 . 15/13 . 14/5 

= 2 

Ps: Rút gọn tới tối giản r tính dễ hơn ế. ;) 

b,19/4 + 37/100 + 1/8 + 132/25 + 5/2 + 37/12=37/15

\(a,-\frac{9}{12}=-\frac{9:3}{12:3}=-\frac{3}{4}\)

\(\frac{-18}{-24}=\frac{\left(-18\right):\left(-6\right)}{\left(-24\right):\left(-6\right)}=\frac{3}{4}\)

\(-\frac{35}{70}=-\frac{35:35}{70:35}=\frac{1}{2}\)

\(-\frac{9}{27}=-\frac{9:9}{27:9}=-\frac{1}{3}\)

\(b,\frac{1313}{4242}=\frac{1313:101}{4242:101}=\frac{13}{42}\)

\(\frac{-353535}{-424242}=\frac{\left(-353535\right):\left(-70707\right)}{\left(-424242\right):\left(-70707\right)}=\frac{5}{6}\)

\(c,\frac{2^3\times4^3\times5^4}{8^2\times25^3\times7}=\frac{2^3\times4^3\times25^2}{8\times8^2\times25^2\times25\times7}\)         ( 4^3 = 8^2 ; 5^4 = 25^2 )

\(=\frac{1}{25\times7}=\frac{1}{175}\)

\(a.\frac{-9}{-12}=\frac{-9:3}{-12:3}=\frac{-3}{-4}.\)

\(\frac{-18}{-24}=\frac{-18:6}{-24:6}=\frac{-3}{-4}\)

\(\frac{-35}{-70}=\frac{-35:35}{-70:35}=\frac{-1}{-2}\)

\(\frac{-9}{-27}=\frac{-9:9}{-27:9}=\frac{-1}{-3}\)

a) \(\frac{-9}{12}=\frac{-9\div3}{12\div3}=\frac{-3}{4}\)

\(\frac{-18}{-24}=\frac{-18\div\left(-6\right)}{-24\div\left(-6\right)}=\frac{3}{4}\)

\(\frac{-35}{70}=\frac{-35\div35}{70\div35}=\frac{-1}{2}\)

\(\frac{-9}{27}=\frac{-9\div9}{27\div9}=\frac{-1}{3}\)

b) \(\frac{1313}{4242}=\frac{1313\div101}{4242\div101}=\frac{13}{42}\)

\(\frac{-353535}{-424242}=\frac{-353535\div\left(-70707\right)}{-424242\div\left(-70707\right)}=\frac{5}{6}\)

c)\(\frac{2^3\times4^3\times5^4}{8^2\times25^3\times7}\)= \(\frac{2^3\times4^3\times5^4}{\left(2^3\right)^2\times\left(5^2\right)^3\times7}\)= \(\frac{2^3\times4^3\times5^4}{2^6\times5^6\times7}\)= \(\frac{2^3\times4^3\times5^4}{2^3\times2^3\times5^2\times5^4\times7}\)= \(\frac{2^3\times2^3}{2^3\times5^2\times7}\)= \(\frac{8}{25\times7}\)= \(\frac{8}{175}\)

(575757/424242 + 575757/565656 + 575757/727272) x 18
= (57/42 + 57/56 + 57/72) x 18 
= 57x3/7 + 57x9/28 + 57/4
= 1596/28
= 57