Audacity Forum

i have a Macbook running 10.5.8 with Audacity 2.0.2.0. I downloaded two MP3 files, the first was 3.1 MB and the second was 1.6 MB and when I combined them in Audacity to make one file and exported it as an MP3 it is now 18.7 MB. What the heck happened????? Is there any way to get it down to 4 or 5 M...