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\(a,3\left(x-5\right)-4\left(x-3\right)=-12\)
\(\Leftrightarrow3x-15-4x+12=-12\)
\(\Leftrightarrow-x=-9\)
\(\Leftrightarrow x=9\)
Vậy x=9
bài 1
a) 155 - 10.(x+1) = 55
=>10 .(x+1) = 100
=>x + 1 = 10
=>x = 9
còn lại tương tự
1/13.58.4+32.26.2+52.10
=52.58+52.32+52.10
=52(58+32+10)=52.100=5200
2/15.37.4+120.21+21.5.12
=60.37+120.21+60.21
=60(37+2.21+21)=60.100=6000
b: \(\Leftrightarrow1-\dfrac{1}{12}+\dfrac{1}{12}-\dfrac{1}{23}+\dfrac{1}{23}-\dfrac{1}{34}+...+\dfrac{1}{89}-\dfrac{1}{100}+x=\dfrac{5}{3}\)
=>x+99/100=5/3
=>x=5/3-99/100=203/300
c: \(\Leftrightarrow\left(\dfrac{1}{11}-\dfrac{1}{13}+\dfrac{1}{13}-\dfrac{1}{15}+...+\dfrac{1}{19}-\dfrac{1}{21}\right)-x+4+\dfrac{221}{231}=\dfrac{7}{3}\)
\(\Leftrightarrow\dfrac{10}{231}-x+4+\dfrac{221}{231}=\dfrac{7}{3}\)
=>5-x=7/3
hay x=8/3
a,[120-12*5]:6
=[120-60]:6
=60:6
=10
b,494-[75+35:5]*2
=494-[75+7]*2
=494-82*2
=494-164
=330
c,1/4+[3/4:1/2]*5/6
=1/4+3/2*5/6
=1/4+5/4
=3/3
d,[360-15*6]:5
=[360-90]:5
=270:5
=54
a) (120-12*5):6= (120-60):6=60:6=10
b) 494-(75+35:5)*2= 494-(75+7)*2=494-82*2=494-164=330
c)1/4+(3/4:1/2)*5/6=1/4+3/2*5/6=1/4+5/4=6/4=3/2
d)(360-15*6):5=(360-90):5=270:5=54
a)\(-x+\left(-53\right)=\left(-42\right)-41\Rightarrow-x+\left(-53\right)=\left(-83\right)\Rightarrow x=\left(-83\right)-\left(-53\right)=-30\)b) \(-12-x=-32+19\Rightarrow-12-x=-13\Rightarrow x=12--13=25\)c)\(453+x=-443+-199\Rightarrow453+x=-562\Rightarrow x=-562-453=-1015\)d)(đề trùng b mk ko làm nha)
e) \(32.\left(-2\right)+x=-120-5.\left(-85\right)\Rightarrow-64+x=545\Rightarrow x=545--64=609\)g)
\(-2x+15.\left(-4\right)=21.\left(-8\right)-12\Rightarrow-2x+-60=-180\Rightarrow2x=-120\Rightarrow x=-60\)
(12*15-x)*1/4=120*1/4
12*15-x=120
180-x=120
x=60
chúc bạn hok tốt
m,