At first, she has 20w flowers
After one year she will have 2*20w = 40w flowers
After two years he will have 2*40w = 80w flowers
A bug eats w flowers per month. In one year there are 12 months, then in two years, there are 2*12 = 24 months. Therefore, in two years, the bug eats 24w flowers.
Finally, 80w - 24w = 56w flowers will be left after 2 years
