Answer:
Luke shaded 20 squares on his hundredths grid. 
= 

Bekka shaded 30 squares on her hundredths grid.
= 

Two decimals greater than Luke's decimal and less than Bekka's decimal.
=> 

Between 0.20 and 0.30 the two decimals are 0.21 and 0.22 and so on.
Therefore, 0.21 and 0.22 are two decimals greater than Luke's decimal and less than Bekka's decimal.