The expression is .

According to addition property of equality: If a = b then a + c = b + c

                       (Add 6 to each side)

                             (Additive inverse property: )

                                      (Add: )

                                            (Additive identity property: )          

check:

To check the solution Substitute the value of  in above expression.

                                 (Subtract: )

The value of

By the number line .