Answer:
150 units
Explanation:
First, you must solve for X.
Because the rectangle and the triangle have equivalent perimeters, you can set the two perimeter formulas equal to one another to solve for X.
The formula for perimeter of a rectangle is P=2(L+W)
The formula for perimeter of a triangle is P=a+b+c (all the sides added)
therefore, 2(L+W)=a+b+c
Now you plug in the values
2(2x+x+12)=2x+x+3+4x
When you solve this, you will get x=21
Next, to find the perimeter, you will plug x into the rectangle perimeter formula.
P=2(2(21)+21+12)
when you solve this, you should get 150 units.
Hope this helped!!!