3x+5=0
3x=0-5
3x=-5
Divide both sides by 3
-1.6666.......
Hope it helps.
As for mod 9, I don't understand.
Answer:

Step-by-step explanation:
Donna's Rate is 
Rico's Rate is 

Cross-Multiply



Donna's Rate is 
Rico's Rate is 

Answer:
Imagine we are to express [
a
,
b
] in set notation
A
=
[
a
,
b
]
, then A
=
{
x ∈ R / a
≤
x
≤
b
}
In this notation we define the characteristics of all x belonging to this set A
....x must be greater or equal to a and simultaneously smaller or equal to b...
Interval notation is other way to say the same but assuming that means the extreme a is IN the interval and means extreme a is not.