1. s0 = 1 for all values except s=0 (which is undefined). Since s=-12, 6*s0 = 6*(-12)0 = 6*1 = 6
2. (a5b)7(a8b)5 = a35b*a40b = a75b [I'm guessing you meant (a8b)5 vice a8b^5]
3. 12y-2 / 4y-8 = 12y8/4y2 = 3y6
4. 361/2 = √36 = ±6 [Guessing again you meant 361/2]
5. (6-2i)+(8-8i) = (6+8)+(-2i-8i) = 14 - 10i
6. 9i*5i = 45i2 = 45*(-1) = -45