Answer:
6 + 3
or 6 - 3
Step-by-step explanation:
x^2 - 12x + 36 = 90
x^2 - 12x - 54 = 0
x = 
a = 1, b= -12, c= -54
6 + 3
or 6 - 3

If I understood correctly and didn't make any mistakes...
Answer:
Bob = 6km/h, Joe = 4km/h
Step-by-step explanation:
Bob walked 6km/h after 3 hours = 18 km
Joe walked 4km/h after 3 hours = 12 km
Finally, their distance is 30 km.
Answer is C.
All real numbers
hope it helps