Change Style Given By Html Using Css : Webdev

Hi, im currently training with some old excersices. I started learning html and css a week ago. Im currently badly stuck at this one. What should i do?
2.3.7 Imagine there is a declaration like class=”oh-no-inline-styles” style=”background:red” and you need to change the background to green without changing the inline style. How could you accomplish this?

Maybe i understood badly the excerises but i tried this (not solved it). Thanks in advance.