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a) 2011 : { 639 : [ 316 – ( 78 + 25 )] : 3 }
= 2011 : { 639 : [ 316 – 103 ] : 3}
= 2011 : ( 639 : 213 : 3 ) = 2011 : (3 : 3 ) = 2011 : 1 = 2011
b) ( 3x – 2 3 ) . 7 = 7 4
3x – 8 = 7 4 : 7
3x – 8 = 7 3
3x – 8 = 343
3x = 343 + 8
3x = 351
x = 351 : 3 = 117
c) (8705 + 5235) – 5x = 3885
13940 – 5x = 3885
5x = 13940 – 3885
5x = 10055
x = 10055 : 5 = 2011
a) 2011 : { 639 : [ 316 – ( 78 + 25 )] : 3 }
= 2011 : { 639 : [ 316 – 103 ] : 3}
= 2011 : ( 639 : 213 : 3 ) = 2011 : (3 : 3 ) = 2011 : 1 = 2011
b) ( 3x – 23) . 7 = 74
3x – 8 = 74 : 7
3x – 8 = 73
3x – 8 = 343
3x = 343 + 8
3x = 351
x = 351 : 3 = 117
c) (8705 + 5235) – 5x = 3885
13940 – 5x = 3885
5x = 13940 – 3885
5x = 10055
x = 10055 : 5 = 2011
Trl:
a) \(2011:\left\{639:\left[316-\left(78+25\right)\right]:3\right\}\)
\(=2011:\left\{639:\left[316-103\right]:3\right\}\)
\(=2011:\left\{639:213:3\right\}\)
\(=2011:1\)
\(=2011\)
b) \(\left(3x-23\right).7=74\)
\(\Rightarrow3x-23=74:7\)
\(\Rightarrow3x-23=10,5\)
\(\Rightarrow3x=10,5+23\)
\(\Rightarrow3x=33,5\)
\(\Rightarrow x=33,5:3\)
\(\Rightarrow11,1\)( Câu này sai đề nha )
c) \(\left(8705+5235\right)-5x=3885\)
\(\Rightarrow13940-5x=3885\)
\(\Rightarrow5x=10055\)
\(\Rightarrow x=10055:5\)
\(\Rightarrow x=2011\)
50 - 3x =20
3x =50-20
3x =30
x =30:3
x =10
Đáp số: x=10
nhớ k mik đó
\(Ư\left(30\right)=\left\{1;2;3;5;6;10;15;30\right\}\\ \Rightarrow x=5\left(B\right)\\ B\left(8\right)=\left\{0;8;16;24;32;...\right\}\\ \Rightarrow x=24\left(B\right)\)
\(20^{3x}=20^{13}:20^4\\ \Leftrightarrow20^{3x}=20^9\\ \Leftrightarrow3x=9\\ \Leftrightarrow x=3\)
\(20^{3x}=20^{13}:\left(4.5\right)^4\\ \Leftrightarrow20^{3x}=20^{13}:20^4\\ \Leftrightarrow20^{3x}=20^9\\ \Rightarrow3x=9\\ \Rightarrow x=9:3\\ \Rightarrow x=3\)
a) 40 - (x - 3) = 25
x-3=40-25
x-3=15
x=15+3
x=18
b)7x+6=20
7x=20-6
7x=14
x=14:7
x=2
=>3x=45
hay x=15
3 x ấy
bài toán như thế