The total cost for roses is 20*5 = $<<20*5=100>>100
Nadia bought 3/4*20 = <<3/4*20=15>>15 lilies.
Each lily costs 5*2 = $<<5*2=10>>10
She used 10*15 = $<<10*15=150>>150 in total to buy lilies.
To buy all the flowers, Nadia used 150+100 = $<<150+100=250>>250
#### 250