Lenny has 20 x 5 = 100 pens. She gave her close friends 100 x 40% = 40 pens. So, 100 - 40 = 60 pens were left. Half of 60 is 60 / 4 = 15 pens. Thus, Lenny has 60 - 15 = 45 pens left.
This justifies what answer for what question? Q & A:
Lenny bought 20 boxes of pens. Each box contained 5 pens. She gave 40% of the pens to her close friends and one-fourth of what's left to her classmates. How many pens were left for Lenny?
45