Forgive me if this is wrong. I haven't done stat in a year, but comment if you need clarification!
The correct answer is 70mm
Answer:
x=0,-3 hope this helps
https://www.symbolab.com/solver/step-by-step/x%5E%7B2%7D%20%2B3x%3D0%20 here this website to show your work hope this helps