a) 15 b)100

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49 ko chia hết cho 15

90 ko chia hết cho 100

a ) 15 

b ) 100

\(\text{a) 49 : x + 56 : x = 7 }\\ 105:2x=7\\ 2x=105:7\\ 2x=15\\ x=\dfrac{15}{2}\)

\(a.49:X+56:x=7\)                    \(b.\left(390:x-90:x\right)=3\)

\(\left(49+56\right):x=7\)                              \(\left(390-90\right):x=3\)

\(105:x=7\)                                        \(300:x=3\)

\(x=105:7=15\)                                 \(x=300:3=100\)

a) 49 : x + 56 : x = 7 

(49 + 56) : x = 7

105 : x = 7

x = 105 : x

= 15

(49+56) : x = 7

105 : x = 7

         x = 105 :7

         x = 15

(49+56):x=7

105:x=7

x=15

x=15 nha bạn

49:x+56:x=7

<=>(49+56):x=7

<=>105:x=7

=>x=105:7

=>x=15

a: x=27

a: x=27

Bài 1: 

\(101\cdot125+101\cdot25-101\cdot50\)

\(=101\cdot\left(125+25-50\right)\)

\(=101\cdot100\)

\(=10100\)

Bài 2: 

\(76\cdot115+56\cdot24+59\cdot24\)
\(=76\cdot115+24\cdot\left(56+59\right)\)

\(=76\cdot115+24\cdot115\)

\(=115\cdot\left(76+24\right)\)

\(=115\cdot100\)

\(=11500\)

5:

a: =>15x=165

=>x=11

b: =>x(x+1)/2=55

=>x^2+x=110

=>x=10

4: =>7x=56

=>x=8

Bài 1:

101•125+101•25+101•50

= 101•(125+25-50)

=101•100

=10100

Bài 2:

76•115+56•24+59•24

= 76•115+24•(56+59)

= 76•115+24•115

= 115•(76+24)

= 115•100

= 11500