Power usage is measured in kilowatt-hours, kwh. after 7 a. m., the power usage on a college campus increases at a rate of 21% per hour. prior to 7 a. m., 15,040 kwh have been used. the university has a daily goal to keep their power usage less than or equal to 100,000 kwh. which of the following inequalities can be used to determine the number of hours, t, after 7 a. m. when the power usage on campus will be less than or equal to 100,000?

After 7 a.m., the power usage on a college campus increases at a rate of 21% per hour.

t be the number of hours

the power usage   increases at a rate of 21% per hour

21% = 0.21, constant rate = 0.21 . So slope = 0.21

Prior to 7 a.m., 15,040 kWh have been used.

At 7.am , power used = 15,040kWh. so our y intercept is 15,040

We use slope  intercept form y=mx+b

slope m = 0.21  and b = 15040

power usage , y = 0.21 t + 15040

The university has a daily goal to keep their power usage less than or equal to 100,000 kWh

Power usage is less than or equal to 100,000

So inequality becomes 0.21t + 15,040 <= 100,000