Find the cost at 7 1/2 per kw-hr:Sept.1: 12,725 kw-hr Oct. 1: 13,814 kw-hr Electric Bill:

If the cost per kw-hr is
[tex]7\text{ }\frac{1}{2}=7.5[/tex]Then, we can calculate the difference betweein the readings of October and September and multiply this for the cost per kw-hr.
So, the total kw-hr between this months is:
[tex]x=13814-12725=1089[/tex]So, if 1 kw-hr costs 7.5, then the total cost will be:
[tex]7.5\cdot1089=8167.5[/tex]Cost of $8,167.50.