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\(\frac{x-12}{77}+\frac{x-11}{78}=\frac{x-74}{15}+\frac{x-73}{16}\)
\(\Leftrightarrow\left[\frac{x-12}{77}-1\right]+\left[\frac{x-11}{78}-1\right]=\left[\frac{x-74}{15}-1\right]-\left[\frac{x-73}{16}-1\right]\)
\(\Leftrightarrow\frac{x-12-77}{77}+\frac{x-11-78}{78}=\frac{x-74-15}{15}+\frac{x-73-16}{16}\)
\(\Leftrightarrow\frac{x-89}{77}+\frac{x-89}{78}=\frac{x-89}{15}+\frac{x-89}{16}\)
\(\Leftrightarrow\frac{x-89}{77}+\frac{x-89}{78}=\frac{x-89}{15}+\frac{x-89}{16}=0\)
\(\Leftrightarrow\left[x-89\right]\cdot\left[\frac{1}{77}+\frac{1}{78}-\frac{1}{15}-\frac{1}{16}\right]=0\)
\(\Leftrightarrow x-89=0\)
\(\Leftrightarrow x=89\)
Vậy x = 89

\(a;\dfrac{2}{3}x-50\%x-\left(-\dfrac{4}{5}\right):1\dfrac{3}{5}=-0,12+1\dfrac{3}{25}\\ \dfrac{1}{6}x+\dfrac{1}{2}=1\Rightarrow\dfrac{1}{6}x=1-\dfrac{1}{2}=\dfrac{1}{2}\\ \Rightarrow x=\dfrac{1}{2}:\dfrac{1}{6}=3\\ b;\left(-1\dfrac{1}{6}+\dfrac{2}{3}-\dfrac{3}{4}\right):x+\left(-1\dfrac{11}{12}\right)\cdot1\dfrac{21}{23}=-6\dfrac{1}{3}\\ -\dfrac{5}{4}:x-\dfrac{11}{3}=-\dfrac{19}{3}\\ -\dfrac{5}{4}:x=-\dfrac{19}{3}+\dfrac{11}{3}=-\dfrac{8}{3}\\ x=-\dfrac{5}{4}:\left(-\dfrac{8}{3}\right)=\dfrac{15}{32}\\ c;50\%x-\dfrac{1}{3}x-\left(-\dfrac{2}{3}\right)^2\cdot\left(-1\dfrac{1}{8}\right)=-119\dfrac{3}{4}+120\dfrac{5}{6}\\ \dfrac{1}{6}x+\dfrac{1}{2}=\dfrac{13}{12}\Rightarrow\dfrac{1}{6}x=\dfrac{13}{12}-\dfrac{1}{2}=\dfrac{7}{12}\\ x=\dfrac{7}{12}:\dfrac{1}{6}=\dfrac{7}{2}\)

\(-\frac{5}{6}x-1\frac{13}{19}:3\frac{7}{19}-\left(-0,12\right)=\left(-\frac{1}{2}\right)^2\)
\(\Rightarrow-\frac{5}{6}x-\frac{32}{19}:\frac{64}{19}+0,12=\frac{1}{4}\)
\(\Rightarrow-\frac{5}{6}x-\frac{1}{2}=\frac{1}{4}-0,12=\frac{13}{100}\)
\(\Rightarrow-\frac{5}{6}x=\frac{63}{100}\)
\(\Rightarrow x=-\frac{189}{250}\)
-5/6x-32/19:64/19+3/25=1/4
-5/6x-32/19×19/64+3/25=1/4
-5/6x-1/2+3/25=1/4
-5/6x-31/50=1/4
-5/6x=1/4+31/50
-5/6x=87/100
x=87/100:-5/6
x=87/100×-6/5
x=-261/250
vậy x=-261/250

\(a.97-7\left(x-8\right)=3\cdot2^4\)
\(97-7\left(x-8\right)=48\)
\(7\left(x-8\right)=97-48\)
\(7\left(x-8\right)=49\)
\(x-8=49:7=7\)
\(x=7+8=15\)
\(b.5x^2-74=51\)
\(5x^2=51+74=125\)
\(x^2=125:5=25\)
\(\Rightarrow x=\pm5\)
\(c.3x+2-3x=216\)
\(0x=214\)
⇒ \(x\in\) rỗng
\(5\left(3x-4\right)^3=40\)
\(\left(3x-4\right)^3=40:5=8\)
⇒ 3x - 4 = 2
⇒ 3x = 2 + 4 = 6
⇒ x = 6 : 3 = 2
a.97−7(x−8)=3⋅24
\(97 - 7 \left(\right. x - 8 \left.\right) = 48\)
\(7 \left(\right. x - 8 \left.\right) = 97 - 48\)
\(7 \left(\right. x - 8 \left.\right) = 49\)
\(x - 8 = 49 : 7 = 7\)
\(x = 7 + 8 = 15\)
\(b . 5 x^{2} - 74 = 51\)
\(5 x^{2} = 51 + 74 = 125\)
\(x^{2} = 125 : 5 = 25\)
\(\Rightarrow x = \pm 5\)
\(c . 3 x + 2 - 3 x = 216\)
\(0 x = 214\)
⇒ \(x \in\) rỗng
\(5 \left(\left(\right. 3 x - 4 \left.\right)\right)^{3} = 40\)
\(\left(\left(\right. 3 x - 4 \left.\right)\right)^{3} = 40 : 5 = 8\)
⇒ 3x - 4 = 2
⇒ 3x = 2 + 4 = 6
⇒ x = 6 : 3 = 2

cái này cồng kềnh nhưng ko khó - >ngại. Bn tính 2/11*13+.... trước bằng cách rút gọn sau đó nhân ra -> dễ
\(0,48x12+0,24+0,12x74\)
=\(0,12x4x12+0,12x2+0,12x74\)
=\(0,12x\left(48+2+74\right)\)
=\(0,12x124\)
=14,88