In January, a city’s snowfall was 5/8 foot below the historical average. In February, the snowfall was 3/4 foot above the historical average. Was the city’s snowfall in the two-month period above or below the historical average? By how much?

The question provides the following information: In January, a city’s snowfall was 5/8 feet below the historical average. Let's assume the snowfall level to be positive if it's above the historical average and negative otherwise.

The data from January gives us a snowfall of -5/8 feet because it was below the average.

We also know in February, the snowfall was 3/4 foot above the historical average. Following our predefined convention, the data from February gives us a snowfall of +3/4 feet.

To know if the city's snowfall during the two-month period was above or below the historical average, we just need to add them, signs included.

If the result is negative, the two-month period showed a snowfall below the historical average.

Let's find the sum of

[tex]\displaystyle -\frac{5}{8}+\frac{3}{4}[/tex]

The LCM of 4 and 8 is 8, thus:

[tex]\displaystyle -\frac{5}{8}+\frac{3}{4}=\frac{-5+2*3}{8}=\frac{1}{8}[/tex]

Since this quantity is positive, we can say the city's snowfall in the two-month period was above the historical average by 1/8 feet.