Question

the perimeter of the rectangle ABCD is 30 cm. Alisa cuts 3 rectangles from that rectangle. the sum of the three perimeter is 20. what is the perimeter of the figure obtained after the cutting

Answer 1

I'll assume that all 3 small rectangles are cut from the same end of the larger rectangle.

If y is the height of the large rectangle, then the three small rectangles have total perimeter of 6y+x, where x is the sum of their widths.

If the width of the larger rectangle is w, then
2(w+y) = 30
w+y = 15

Now, 2x+6y = 20
x = 10-3y = 10-3(15-w) = 3w-45

The perimeter of the figure after cutting is p=30-(x+y)

So, consider the possibilities.
y=1 (big rectangle is 14x1) x=7 so p=30-8=22
y=2, x=4, 24
and so on

Maybe there is more to the problem than you gave.