The sentence is one third equals negative seven times a number.

The word “times” indicates the symbol " "

The word “equals” indicates the symbol “=”

The word “negative” indicates the symbol “"

Let n = number.          

Rewrite the sentence into equation, \ \

\ \

The equation is 

According to division property of equality:

For any number a, b and c, If a = b then .

 (Divide each side by  )

                     (Cancel common terms)

                               (Multiply:)

\ \

Verify:

To check the solution, substitute in original equation.

\ \

                                     (Multiply:  )

Compare the values, the equation is true. The solution is . \ \

The solution is .