Answer: 
 
24 
 
Step-by-step explanation: 
 
6 ÷ 15 = 0.4 
 
X to Y = 20 × 0.4 = 8 
 
Y to Z = 25 × 0.4 = 10 
 
Perimeter: a + b + c 
 
6 + 8 + 10 = 24 
 
Even I am surprised by what I wrote. Hopefully, it is right and helps you ^-^ Please comment if you have any questions.
-Tay did this