The expression is .

According to addition property of equality: if a = b, then a + c = b + c.

     (Add 80 to each side)

            (Additive identity property: 0 + 80 = 80) \ \

                             (Additive inverse property:  )

According to division property of equality: if , then .

                           (Divide each side by negative 2)

                                   (Cancel common terms)

                                   (Divide: )

                        (Take square roots of each side)

Product property of square roots:

For nonnegative real numbers a and b,

Rewrite the (-1) using imaginary unit; that is where i² = -1.

            (Find the square root: )

              (Simplify)

The value of x.