Bài 1:
a) $\frac{19}{24}$ - $\frac{49}{25}$ + $\frac{5}{24}$ - $\frac{51}{25}$
= ($\frac{19}{24}$ + $\frac{5}{24}$) + (-$\frac{49}{25}$ - $\frac{51}{25}$)
= 1 - 4
= -3
b) 46.(51 - 27) - 51.(45 - 27)
= 46 . 24 - 51 . 18
= 1104 - 918
= 186
c) $\frac{-5}{-15}$ + $\frac{9}{7}$ + $\frac{1}{-3}$ - $\frac{-276}{14}$
= $\frac{5}{15}$ + $\frac{9}{7}$ - $\frac{1}{3}$ + $\frac{276}{14}$
= $\frac{70}{210}$ + $\frac{270}{210}$ - $\frac{70}{210}$ + $\frac{4140}{210}$
= $\frac{70+270-70+4140}{210}$
= $\frac{4410}{210}$ = 21
d) $\frac{5.6+6.(-3)}{18.5}$
= $\frac{30-18}{90}$
= $\frac{12}{90}$ = $\frac{2}{15}$
Bài 2:
a) 23 + 2(x - 3) = 15
2(x - 3) = 15 - 23
2(x - 3) = -8
x - 3 = -8 : 2
x - 3 = -4
x = -4 + 3
x = -1
Vậy x = -1
c) $\frac{9}{x}$ = $\frac{-35}{105}$
Ta có:
x = $\frac{105.9}{-35}$
x = -27
Vậy x = -27
