please help me with this quickly and explain your answer

Answer:
D. x = 10
Step-by-step explanation:
Perimeter = the sum of all sides lengths
Perimeter = 30 (in this case)
so...
[tex]((x-5)+x)2=30[/tex]
Step 1. Dividing 3 to both sides
[tex]((x-5)+x)=15[/tex]
Step 2. Add 5 to both sides
[tex]x+x=20[/tex]
Step 3. Solve for x
Since x + x = 20, to solve for one of the x means solving for the other x
so since 2 x's are being added with the same value, divide 20 by 2.
x = 10