The percentage of new beakers is given in the problem - 20% of the beakers. 20% = 20 / 100, so you should shade 20 squares.
Next, we'll set up a proportion to find the number of beakers that are new.
(percentage as a fraction) = ? new beakers / the total amount of beakers
20 / 100 = x / 55
100x = 1100
x = 11 new beakers
Hope this helps!! :)