Answer:

Solution:

We're going to use Arithmetic sequence by determining first the common difference,

since, at first she has gained Php.500, and 2nd Php1000, then common difference is 500 or d = 500

500, 1000, 1500, 2000,...we can also use the formula to find the 8th and 10th sales period of time or term

Solving for the 8th sales

 =  + (n - 1) d    (Equation)

 =  500 + (8- 1) 500

     =  500 + 7(500)

     =   500 + 3500

      = 4000, therefore the 8th sales is Php.4000

For the 10th sales period of time, the what we did for first

 =  + (n - 1) d

 =  500 + (10- 1) 500

      =  500 + 9(500)

      = 500 + 4500

      = 5000

Hence, the 10th sales is Php5000.

That is,

500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000

Thank you!

I hope you have got an idea.

Step-by-step explanation: