Is this a question? Or what is the question if you first said it?
6x+19.98=200
200-19.98=6x
X= 200-19.98/6
= solve for it.
Answer: 37
Step-by-step explanation:
Given : Significance level : 
Critical value : 
margin of error : E= 1 mile per gallon
Population standard deviation:
miles per gallon.
We know that when the population standard deviation is known then the formula to find the sample size is given by :

[Round to the next whole number.]
Hence, the required number of automobiles should be used in the test = 37