Don't let fractions fool you.

of a tank in

an hour is equal to:
1/12 of a tank in 20 minutes.
Thus we know in an hour, an oil company can fill 3/12 of a tank (60 minutes in an hour).
3 x 4 = 12, and 12/12 = 1(a whole tank), so we multiply 1 (hour) by 4.
Our answer is that it takes 4 hours to fill a tank.
If we plot the data on the graph, we can see that the
data is skewed to the right (positive skew) and there is an outlier. In skewed
data and presence of outlier, the median is most commonly used measure of
central tendency. This is because a positive skew would result in a positive
bias to the mean. Meaning that it would be a lot larger than the median and not
really representing the actual central tendency. The median however is less
affected by the skew and outliers.
Answer: Median, because the data are skewed and there is
an outlier
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You can simply put the equation as 9x = 36 and divide by 9, then x = 4