I think it would be **-12, use the infinite geometric series equation :**

For this equation, it would be: x / ( 1 - 0.5x^2)

set this equation to equal -12, you will get 2 different x answers x = -4/3 and x = 3/2, however, one is eliminated

**x = - 1 (1/3 )**

**Credit : Melody **

**Link : https://web2.0calc.com/questions/kevin-kangaroo-begins-hopping-on-a-number-line-at**