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a) (x.7 + 8) : 5 = 10
x.7 + 8 = 10.5
x.7 + 8 = 50
x.7 = 50 - 8
x.7 = 42
x = 42 : 7
x = 6
b) (x + 5).19 : 13 = 57
(x + 5).19 = 57 . 13
(x + 5).19 = 741
x + 5 = 741 : 19
x + 5 = 39
x = 39 - 5
x = 34
c) 4.(36 - 4.x) = 64
36 - 4x = 64 : 4
36 - 4x = 16
4x = 36 - 16
4x = 20
x = 20 : 4
x = 5
d) 7,6 : 19 . x = 3,2
0,4 . x = 3,2
x = 3,2 : 0,4
x = 8
e) (x : 2 + 50) : 5 = 12
x : 2 + 50 = 12 . 5
x : 2 + 50 = 60
x : 2 = 60 - 50
x : 2 = 10
x = 10 . 2
x = 20
g) 280 : (17 + 3.x) = 4
17 + 3x = 280 : 4
17 + 3x = 70
3x = 70 - 17
3x = 53
x = 53/3
h) 6.(28 - 8.x) = 72
28 - 8x = 72 : 6
28 - 8x = 12
8x = 28 - 12
8x = 16
x = 16 : 8
x = 2
i) (x - 15) : 3 : 12 = 6
(x - 15) : 3 = 6 . 12
(x - 15) : 3 = 72
x - 15 = 72 . 3
x - 15 = 216
x = 216 + 15
x = 231
a: \(=\left(15-6-\dfrac{13}{18}\right):\dfrac{298}{27}-\dfrac{17}{8}:\dfrac{51}{40}\)
\(=\dfrac{149}{18}\cdot\dfrac{27}{298}-\dfrac{5}{3}=\dfrac{3}{2}-\dfrac{5}{3}=\dfrac{9-10}{6}=\dfrac{-1}{6}\)
b: \(=\dfrac{-16}{5}\cdot\dfrac{-15}{64}+\dfrac{-22}{15}:\dfrac{11}{2}\)
\(=\dfrac{3}{4}-\dfrac{4}{15}=\dfrac{29}{60}\)
c: \(=\dfrac{-7}{9}\left(\dfrac{4}{11}+\dfrac{7}{11}\right)+5+\dfrac{7}{9}=\dfrac{-7}{9}+\dfrac{7}{9}+5=5\)
d: \(=\dfrac{1}{2}\cdot\dfrac{4}{3}\cdot10\cdot\dfrac{1}{5}\cdot\dfrac{3}{4}=1\)
e: \(=\dfrac{4}{25}+\dfrac{11}{2}\cdot\dfrac{5}{2}+\dfrac{-23}{4}=\dfrac{204}{25}\)
Câu 1:
a: x+2,57=14,25-6,3
=>x+2,57=7,95
=>x=5,38
b: 12,9-x=4,2+2,4
=>12,9-x=6,6
hay x=6,3
a) \(\left(x.7+8\right):5=10\)
\(x.7+8=10.5\)
\(x.7+8=50\)
\(x.7=50-8\)
\(x.7=42\)
\(x=42:7\)
\(x=6\left(tm\right)\)
Vậy ......................
b) \(\left(x+5\right).19:13=57\)
\(\left(x+5\right).19=57.13\)
\(\left(x+5\right).19=741\)
\(x+5=741:19\)
\(x+5=39\)
\(x=39-5\)
\(x=34\left(tm\right)\)
Vậy ..................
c) \(4\left(36-4x\right)=64\)
\(36-4x=64:4\)
\(36-4x=18\)
\(4x=36-18\)
\(4x=18\)
\(x=\dfrac{18}{4}\)
Vậy ....................
d) \(7,6:1,9.x=3,2\)
\(4x=32\)
\(x=32:4\)
\(x=8\left(tm\right)\)
Vậy ................
\(1\frac{13}{15}\times\left(-0,5\right)^2\times3+\left(\frac{8}{15}-1\frac{19}{50}\right)\)
\(=\frac{28}{15}\times\frac{1}{4}\times3+\frac{8}{15}-\frac{69}{50}\)
\(=\frac{7}{5}+\frac{8}{15}-\frac{69}{50}\)
\(=\frac{83}{150}\)
15(x-8)-3,2=50+2017
=>15x-120-3,2=50+2017
=>15x=2190,2
=>x=146,01
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