Answer:
$1200.
Step-by-step explanation:
We have been given that Kiersten runs a website that helps people learn programming. Every month, Kiersten receives a subscription fee of $10 from each of the subscribers to her website.
Let us find number of subscriber that will pay this month Kiersten for her online business.
Last month, the website had 100 subscribers. This month, 30 new members joined the website, and 10 members cancelled their subscription, therefore, number of subscriber this month will be
subscribers.
To find amount that Kiersten will receive from online business we will multiply 10 by 120.
![\text{Kiersten will earn from online business}=120\cdot 10](https://img.qammunity.org/2019/formulas/mathematics/middle-school/zg2ssfrwaar6fkefkxp6hzxjuqb43mm7vk.png)
Therefore, Kiersten will earn $1200 from online business this month.