Solve x2 – 12x + 59 = 0 for x.

x = -12 + _/85

x= -6 + _/23i

x= 6 + _/ 23i

x= 12 + _/85

Using the quadratic formula, you can solve this quite easily.
a      b       c
x² - 12x + 59 = 0              a(1)...b(-12)c(59)

(-b +/- √b² - 4ac) / (2a)      (substitute the values for a, b, and c)
(-(-12) +/- √ (-12)² - 4 (1) (59)) / 2(1)
(12 +/- √-92) / 2                  ( √-92 can be written as √-1√4√23)
(12 +/- √-1√4√23) / 2          (√-1 = i and √4 = 2)

6 +/- 23i