Answer:
[tex]\huge\boxed{P_\triangle=10y+1}[/tex]
Step-by-step explanation:
The formula of a perimeter of a triangle:
[tex]P_\triangle=a+b+c[/tex]
We have:
[tex]a=3y+5,\ b=6y,\ c=y-4[/tex]
Substitute:
[tex]P_\triangle=(3y+5)+(6y)+(y-4)=3y+5+6y+y-4[/tex]
Combine like terms:
[tex]P_\triangle=(3y+6y+y)+(5-4)=10y+1[/tex]
