Answer:

Step-by-step explanation:
C the value of m and b doesn't affect the sign of the x-int
m is the slope of the line and b is the y-int
Consider the given equations:
The first equation is as:

So, 
= 
Multiplying the given fractions, we get as
= 
Now, consider the second equation as:

Multiplying by '3' to both the sides of the equation, we get


So, the number which best completes both the equations is
.
4% =.04
20*.04= 0.8
The sales tax is 80 cents.
I hope this helps!
~kaikers