First we shade first two columns of first gird box.
Each column represetns one ones.
So, two columns would represent 2 ones.
Now, we would shade 20 small boxes of another gird box.
Each small box would represent a tenth.
Because we shaded 20 small boxed of tenths, so 20 boxes would make 20 tenths.
So, the shaded figure represents 2 ones is the same as 20 tenths .