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a) 15 + x + 27 + 53 = 201
=> x + ( 15 + 27 + 53 ) = 201
=> x + 95 = 201
=> x = 201 - 95
=> x = 106
Vậy x = 106
b) 50 * x + 20 617 = 80 617
=> 50 * x = 80 617 - 20 617
=> 50 * x = 60 000
=> x = 60 000 : 50
=> x = 1 200
Vậy x = 1 200
c) x * 25 + x * 35 = 90 * 360
=> x * ( 25 + 35 ) = 32 400
=> x * 60 = 32 400
=> x = 32 400 : 60
=> x = 540
Vậy x = 540

Lời giải:
\((50\times 60\times 70\times 80):(15\times 25\times 28\times 20)\\ =(50:25)\times (60:15)\times (70:28)\times (80:20)\\ =2\times 4\times \frac{5}{2}\times 4=80\)

b ) \(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}=\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}=\left(\frac{1}{2}-\frac{1}{3}\right)+\left(\frac{1}{3}-\frac{1}{4}\right)+\left(\frac{1}{4}-\frac{1}{5}\right)+\left(\frac{1}{5}-\frac{1}{6}\right)+\left(\frac{1}{6}-\frac{1}{7}\right)=\frac{1}{2}-\frac{1}{7}=\frac{5}{14}\)
215 - 15 x { 25 - 15 : [ 3 x 45 - 3 x ( 50 - 2 x 3 ) ] }
= 215 - 15 x { 25 - 15 : [ 3 x 45 - 3 x 44 ] }
= 215 - 15 x { 25 - 15 : 3 }
= 215 - 15 x 20
= 215 - 300
= -85
b) \(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}\)
\(=\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+\frac{1}{5\cdot6}+\frac{1}{6\cdot7}\)
\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\)
\(=\frac{1}{2}-\frac{1}{7}=\frac{5}{14}\)

25 x10 x8 x 4 x25 x50
=25 x 10 x 2 x4 x4 x25 x50
=(25x4) x(25x4) x x ( 50 x 2) x 10
=100 x 100 x 100 x10
=10000000

(25% : 0,45 + 50% x 50) x (0,15% - 0,75 x 0,2%)
=(25% : 0,45 + 50% x 50) x (0,15% - 0,15%)
=(25% : 0,45 + 50% x 50) x 0
=0


a) 17 x 25 + 25 x 33 +25 x 50 = 25 x (17 + 33 + 50)
= 25 x 100 = 2500
b) 125 x 15 -25 x 15 = 15 x (125 - 25)
= 15 x 100 = 1500

x = 50 - 15 - 25
x = 10
@Nghệ Mạt
#cua