n - a number
the sum of a number and six: n + 6
eleven times the sum of a number and six: 11 · (n + 6)
Eleven times the sum of a number and six is -66:
11 · (n + 6) = -66
11(n + 6) = -66 divide both sides by 11
n + 6 = -6 subtract 6 from both sides
n = -12
