**-18**

Eleven numbers are: x1 to x11

x1*x2*x3=120, x2*x3*x4=120, x3*x4*x5=120 => every 3 numbers repeat in this sequence as:

x1, x2, x3, x1, x2, x3, x1, x2, x3, x1, x2

As 2 numbers are given the three repeated numbers will be -4, -5, 6

The sum of eleven numbers will be equal to 4*(x1+x2+x3)-x3=4*(-3)-6=**-18**