The equation is
.
(Write the equation)
Apply subtraction property of equality: if
.
(Subtract 6 from each side)
(Rewrite as the summation)
(Apply additive inverse property:
)
(Apply additive identity property:
)
(Add:
)
Check whether
is a solution.

(Write the equation)
(Substitute 
)
(Apply additive inverse property:
)
is a solution.
The solution is 
.