Answer:

Step-by-step explanation:
8x+9=0
8x=-9

or

,



, 
Answer:
12 seconds.
Step-by-step explanation:
If you put it like 15/9 = 20/x, then cross multiply and divide you do 9 times 20 you get 180, then you divide 180 by 15 and you get 12. Hope this helps!
Answer:
10 dollars
Step-by-step explanation:
4 + 6 = 10 which mean 10 dollars spent