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= 3x2x28 + 3x6x14 + 3x8x11 - 3x2x4
= 3x 56 + 3x 84 + 3x88 - 3x8
=3x(56+84+88-8)
=3x220
=660
6 x 28 +18 x 14 +24 x 11 - 6 x 4
= 168 + 252 + 264 - 24
= 420 +264 -24
= 684 -24
= 660

\(32\times25+18\times100-50\times12\)
\(=800+1800-600\)
\(=2000\)
\(56\times45+28\times98+56\times6\)
\(=2520+2744+336\)
\(=5600\)
32 x 25 + 18 x 100 - 50 x 12 = 32 x 25 + 18 x 4 x 25 - 25 x 2 x 12
= 32 x 25 + 72 x 25 - 25 x 24
= ( 32 + 72 - 24 ) x 25
= 80 x 25
= 2000
56 x 45 + 28 x 98 + 56 x 6 = 56 x 45 + 28 x 2 x 49 + 56 x 6
= 56 x 45 + 56 x 49 + 56 x 6
= 56 x ( 45 + 49 + 6 )
= 56 x 100
= 5600

C1 : 5 x 1250 - 25 x 50
= 6250 - 1250
= 5000
C2:5 x 1250 - 25 x 50
= 5 x 1250 - (25 x 5 x 10)
= 5 x (1250 - 25 x 10)
= 5 x (1250 - 250)
= 5 x 1000
= 5000

200 - 18 : ( 372 : 3 : X - 1 ) - 28 = 166
200 - 18 : ( 372 : 3 : X - 1 ) = 166 + 28
200 - 18 : ( 372 : 3 : X - 1 ) = 194
200 - 18 : ( 124 . X - 1 ) = 194
18 : ( 124 . X - 1 ) = 200 - 194
18 : ( 124 . X - 1 ) = 6
124 . X - 1 = 18 : 6
124 . X - 1 = 3
124 . X = 3 + 1
124 . X = 4
X = 4 : 124
X = 1/31.
200-18:(372:3:x-1)-28=166
200-18:(372:3:x-1)=166+28
200-18:(372:3:x-1)=194
18:(372:3:x-1)=200-194
18:(372:3:x-1)=6
372:3:x-1=18:6
372:3:x-1=3
124:x-1=3
124:x=3+1
124:x=4
x=124:4
x=31

\(a)\frac{5}{12}+\frac{3}{14}+\frac{7}{12}=\left(\frac{5}{12}+\frac{7}{12}\right)+\frac{3}{4}=1+\frac{3}{4}=\frac{7}{4}\)
\(b)\frac{15}{14}\times\frac{17}{18}\times\frac{28}{15}=\frac{15\times17\times28}{14\times18\times15}=\frac{17}{9}\)
\(c)\frac{5}{8}\times\frac{5}{4}+\frac{5}{4}\times\frac{3}{8}=\frac{5}{4}\times\left(\frac{5}{8}+\frac{3}{8}\right)=\frac{5}{4}\times1=\frac{5}{8}\)

\(a)\frac{5}{12}+\frac{3}{14}+\frac{7}{12}=\left(\frac{5}{12}+\frac{7}{12}\right)+\frac{3}{4}=1+\frac{3}{4}=\frac{7}{4}\)
\(b)\frac{15}{14}\times\frac{17}{18}\times\frac{28}{15}=\frac{15\times17\times28}{14\times18\times15}=\frac{17}{9}\)
\(c)\frac{5}{8}\times\frac{5}{4}+\frac{5}{4}\times\frac{3}{8}=\frac{5}{4}\times\left(\frac{5}{8}+\frac{3}{8}\right)=\frac{5}{4}\times1=\frac{5}{8}\)
~Học tốt~

200 - 18 : ( 372 : 3 : X -1 ) -28 = 166
suy ra 18 : ( 372 : 3 : X - 1 ) - 28 = 200 -166 = 34
Suy ra 18 : ( 372 : 3 : X -1 ) = 34 + 28 = 62
Suy ra 372 : 3 : X -1 = 18 : 62
Suy ra 124 : x -1 = 9/31
Suy ra 124 : x = 9/31 +1 =40/31
Suy ra X = 124 : 40/31
Suy ra X = 961/10 = 96,1
X x 2 -X x 18= 1250
X x( 28 -18 ) = 1250
X x 10 =1250
X =1250 : 10
X = 125
X x 28 - X x 18 = 1250
X x ( 28 - 18 ) = 1250
X x 10 = 1250
X = 1250 : 10
X = 125
Vậy X = 125
_HT_