Question

Answer 1

x=-6

_HT_

Answer 2

x= -6

_HT_

Answer 3

\(\Leftrightarrow21x=7x-84\)

\(\Leftrightarrow21x-7x+84=0\)

\(\Leftrightarrow14x=-84\)

\(\Leftrightarrow x=-6\)

Answer 4

\(\dfrac{3x}{21}=\dfrac{x-12}{21}\)

=> 3x=x-12

3x-x=x-12-x

2x=-12

x=-6

Answer 5

\(\dfrac{x}{7}=\dfrac{x-12}{21}\)

\(⇔21x=7(x-12)\)

\(⇔21x-7x=-84\)

\(⇔14x=-84\)

\(⇔x=-6\)