Answer:
a=0
b=2
Step-by-step explanation:
It will take her 12 minutes to run a full mile
your answer option is option 3.
6 and 7
One reason would be if you did not know the answer so you could do
4-5=x
another reason would be if the problem gave you the answer but not one of the things to get the answer
4-x=-1
not sure if that is what you want but I hope this helped