Bài 5:
c, 17$\frac{3}{4}$ - (2$\frac{4}{7}$ + 13$\frac{3}{14}$) + 5$\frac{4}{7}$
= 17,75 - $\frac{221}{14}$ + $\frac{39}{7}$
= $\frac{211}{28}$
d, (25$\frac{29}{33}$ - 4$\frac{7}{6}$) - (20$\frac{29}{33}$ - 5$\frac{7}{8}$
= $\frac{1367}{66}$ - $\frac{3961}{264}$
= $\frac{137}{24}$
e, 0,75 - $\frac{5}{7}$.$\frac{4}{11}$ - $\frac{4}{11}$.$\frac{12}{17}$
= 0,75 - $\frac{4}{11}$($\frac{5}{17}$ + $\frac{12}{17}$)
= 0,75 - $\frac{4}{11}$
= $\frac{17}{44}$
g, $\frac{15}{34}$ + $\frac{7}{21}$ + $\frac{19}{34}$ - $\frac{5}{15}$ + $\frac{3}{7}$
=($\frac{15}{34}$ + $\frac{19}{34}$) + $\frac{1}{3}$ - $\frac{1}{3}$ + $\frac{3}{7}$
= 1 + $\frac{3}{7}$
= $\frac{10}{7}$
h, ($\frac{3}{13}$ : $\frac{11}{6}$ + $\frac{3}{13}$ : $\frac{11}{5}$) - $\frac{2}{13}$
=($\frac{3}{13}$ × $\frac{6}{11}$ + $\frac{3}{13}$ × $\frac{5}{11}$) - $\frac{2}{13}$
={$\frac{3}{13}$($\frac{6}{11}$ + $\frac{5}{11}$) - $\frac{2}{13}$
=$\frac{3}{13}$ - $\frac{2}{13}$
=$\frac{1}{13}$
i, $\frac{5}{24}$.$\frac{7}{2}$ + $\frac{7}{2}$.$\frac{38}{34}$ - $\frac{7}{2}$
=$\frac{7}{2}$($\frac{5}{34}$ + $\frac{38}{34}$ - 1)
= $\frac{7}{2}$. $\frac{9}{34}$
= $\frac{63}{68}$
Bài 6:
a, $\frac{-3}{4}$ + $\frac{1}{4}$ : x = -3$\frac{3}{4}$
⇔$\frac{1}{4}$ : x = -3
⇔x = $\frac{-1}{12}$
b, 2x : 5/7 - 1/7 = -1$\frac{9}{14}$
⇔2x : 5/7 = -3/2
⇔2x = -15/14
⇔x = -15/28
c,0,75x - 25%x = 0,5
⇔x(0,75 - 0,25) = 0,5
⇔0,5x = 0,5
⇔x = 1
d, $\frac{3}{4}$(x-$\frac{1}{2}$)=$\frac{1}{2}$(3-2x)
⇔$\frac{3}{4}$x - 3/8 = 3/2 - x
⇔$\frac{3}{4}$x + x = 3/2 + 3/8
⇔$\frac{7}{4}$x = 15/8
⇔x = 15/14
e, $\frac{2}{5}$x - (-3/5) = -1$\frac{2}{5}$x - 7/10
⇔$\frac{9}{5}$x = -13/10
⇔x = -13/18
g, $\frac{3}{4}$(x - 1/2)² = 1/3
⇔(x - 1/2)² = $\frac{4}{9}$
⇔x - 1/2 = 2/3
⇔ x = 7/6
h, (-1/2 - 50%x)² = 5$\frac{4}{9}$
⇔ -1/2 - 1/2x = 7/3
⇔-1/2x = 17/6
⇔x = -17/3
i, (3 - $\frac{1}{2}$x)(0,25x - 1) = 0
⇔\(\left[ \begin{array}{l}3-\frac{1}{2}x = 0\\0,25x - 1 =0\end{array} \right.\)
⇔\(\left[ \begin{array}{l}1/2x =3\\0,25x = 1\end{array} \right.\) => \(\left[ \begin{array}{l}x=6\\x=4\end{array} \right.\)
