(7/4+ 1/10) nhan 12?
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a) (x.7 +8):5=10
x.7 +8= 10.5=50
x.7= 50-8=42
x= 42:7=6
b) 280: (7+3.x)=4
7+3.x= 4.280= 1120
3.x= 1120-7 =1113
x= 1113: 3= 371
c) (x.5) .19:13= 57
(x.5). 19= 57.13= 741
x.5= 741: 19= 39
x= 39:5 =7,8
d) 6.(28-8).x = 72
20.x= 72:6= 12
x= 12: 20= 0,6
e) 4. (36-4.x)= 3,2
36-4.x= 32:4= 0,8
-4.x= 0,8- 36= -35,2
x= -35,2 : -4 = 8,8
f) (x-15).3 :12= 6
(x-15).3 = 6. 12= 72
x-15= 72: 3= 24
x= 24+ 15= 39
g) (x:4+ 6) . 7 = 70
x:4+6= 70:7= 10
x:4= 10-6= 4
x= 4.4 = 16
h) (x:2+50) :5= 12
x:2+ 50= 12.5= 60
x:2= 60-50= 10
x= 10.2=20
l) 5.(7+3.x)= 140
7+3.x= 140:5 = 28
3.x= 28-7 =21
x= 21: 3= 7
k cho mình nhe
\(\left[12\cdot15-x\right]\cdot\frac{1}{4}=120\cdot\frac{1}{4}\)
\(\Leftrightarrow\left[180-x\right]\cdot\frac{1}{4}=30\)
\(\Leftrightarrow180-x=30:\frac{1}{4}\)
\(\Leftrightarrow180-x=120\)
\(\Leftrightarrow x=60\)
4 x 5 x 6/8 x 10 x 12
= 4 x 5 x 3/4 x 10 x 12
3 x 5 x 10 x 12
= 1800
\(\dfrac{12}{7}\times\dfrac{4}{13}+\dfrac{12}{14}\times\dfrac{14}{26}-\dfrac{6}{7}\times\dfrac{2}{13}\)
= \(\dfrac{6}{7}\times\dfrac{4\times2}{13}+\dfrac{6}{7}\times\dfrac{7}{13}-\dfrac{6}{7}\times\dfrac{2}{13}\)
= \(\dfrac{6}{7}\times\left(\dfrac{8}{13}+\dfrac{7}{13}-\dfrac{2}{13}\right)\)
= \(\dfrac{6}{7}\times1\) = \(\dfrac{6}{7}\)
\(\frac{7}{3}+\frac{13}{3}=\frac{7+13}{3}=\frac{20}{3}\)
\(\left(\dfrac{7}{4}+\dfrac{1}{10}\right)\text{x}12=\left(\dfrac{35}{20}+\dfrac{2}{20}\right)\text{x}12=\dfrac{37}{20}\text{x}12=37\text{x}\dfrac{3}{5}=\dfrac{111}{5}\)