a) \(\frac{1}{2} - \frac{1}{2} : x = \frac{3}{4}\)

\(\frac{1}{2} : x = \frac{1}{2} - \frac{3}{4}\)

\(\frac{1}{2} : x = \frac{- 1}{4}\)

\(x = \frac{1}{2} : \&\text{nbsp}; \frac{- 1}{4}\)

\(x = - 2\)

b) \(\frac{x - 1}{15} = \frac{3}{5}\)

\(\frac{x - 1}{15} = \frac{9}{15}\)

\(x - 1 = 9\)

\(x = 10\)

c) \(x + 2 , 5 = 1 , 4\)

\(x = 1 , 4 - 2 , 5\)

\(x = - 1 , 1\)

a)A= 2,34+ 5,35+ 7,66+ 4,65 c)C= 1/3 - 1/3 : 3/4

A= (2,34+ 7,66) +( 5,35+4,65) C= 1/3 - 1/3 . 4/3

A= 10,00+ 10,00 C=1/3 - 4/9

A=20,00 Vậy A= 20,00 C=3/9 - 4/9

b)B=2,13.75+ 2,13.25 C= -1/9 Vậy C = -1/9

B=2,13.(75+25)

B= 2,13.100

B=213 Vậy B= 213