(10x+5)4 = 30x + 3x + 6x +30
40x + 20 = 39x + 30
X = 10
perimeter of the square= 420
perimeter of the triangle= 420
This is a proportion problem that involves cross-multiplication
Set your problem up like so:

=

Now cross multiply
2,000 x 3 = 6,000
now you're left with 5x = 6,000
Now divide by 5 on both sides
Answer is 1,200