Can someone please help me

Answer:
20
Step-by-step explanation:
If the two triangles are similar, then corresponding sides must share a constant ratio. This means that:
[tex]\dfrac{10}{6}=\dfrac{25}{15}=\dfrac{x}{12}[/tex]
Let's use the second ratio:
[tex]\dfrac{25}{15}=\dfrac{x}{12}[/tex]
Multiply both sides by 12:
[tex]\dfrac{25\cdot 12}{15}=x \\\\x=20[/tex]
Hope this helps!