a) 15

b) 100

a) 15

b) 100 

~HT~

k cho mik nha

\(a,49:x+56:x=7\)

\(\Rightarrow\left(49+56\right):x=7\)

\(\Rightarrow105:x=7\)

\(\Rightarrow x=15\)

Vậy: \(x=15\)

\(b,390:x-90:x=3\)

\(\Rightarrow\left(390-90\right):x=3\)

\(\Rightarrow300:x=3\)

\(\Rightarrow x=100\)

Vậy: \(x=100\)

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

\(\left(390:x-90:x\right)=3\)
\(\Rightarrow\left(390-90\right):x=3\)
\(\Rightarrow300:x=3\)
\(\Rightarrow x=300:3\)
\(\Rightarrow100\)

(390:x-90:x)=3

(390-90):x=3

300:x=3

x=300:3

x=100

(390:x-90:x)=3

(390-90):x=3

300:x=3

x=300:3

x=100

a: x=27

a: x=27

a: Ta có: \(\dfrac{x-2}{x-1}=\dfrac{x+4}{x+7}\)

\(\Leftrightarrow x^2+5x-10=x^2+3x-4\)

\(\Leftrightarrow2x=6\)

hay x=3

15 nha

49 : x + 56 : x = 7

( 49 + 56 ) : x = 7

105 : x = 7

x = 105 : 7

x = 15

k mk nha

Mk cảm ơn các bạn nhiều

Thank you very much

( ^ _ ^ )

       49 : x + 56 : x = 7

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

<=>105 : x = 7

<=> x = 15.