I need help with this exercise please. What I need to know is the measure of one side of the square. Sorry for the language of the exercise

Answer:
[tex]\boxed{\sf \ \ x=6 \ \ }[/tex]
Step-by-step explanation:
Hello,
BMN and NPC are two similar triangles so
[tex]\dfrac{BM}{MN}=\dfrac{NP}{PC}\\\\ \dfrac{10-x}{x}=\dfrac{x}{15-x}\\\\<=>(15-x)(10-x)=x^2\\\\<=>150-25x+x^2=x^2\\\\<=>25x=150\\\\<=>x=6[/tex]
espero que esto ayude