Question

Tìm x, biết

a) \(\frac{x}{4}\)= \(\frac{21}{28}\)

b) \(\frac{2x}{5}\)= \(\frac{-24}{10}\)

Answer 1

a)\(\frac{x}{4}=\frac{21}{28}\)

x . 28 = 4.21

x.28 = 84

x = 84:28

x = 3

Vậy x = 3

b)\(\frac{2x}{5}=\frac{-24}{10}\)

2x.10=5.(-24)

2x.10= -120

2x = -120 :10

2x= -12

x= -12 : 2

x= -6

Vậy x = -6

Answer 2

a,\(\frac{x}{4}\)=\(\frac{21}{28}\)

\(\Leftrightarrow\)28x=21.4

\(\Leftrightarrow\)28x=84

\(\Leftrightarrow\)x=3

Vậy x=3

b, \(\frac{2x}{5}\)=\(\frac{-24}{10}\)

\(\Leftrightarrow\)2x.10=-24.5

\(\Leftrightarrow\)20x=-120

\(\Leftrightarrow\)x=-6

Vậy x=-6

Chúc bn hk tốt