Answer:
m a g i c t h a t ' s h o w
The line segment is translated to the left across the square.
although an image would be useful
Perfect squares can be divided and multiplied by the same number to get the same number. For example 25/5=5. 5*5=25.
4/2=2, 2*2=4
1/1=1, 1*1=1
9/3=3, 3*3=9
16/4=4, 4*4=16.
Hence the perfect squares.
30-10=20
20-10=10
or
10+20=30
