On Monday she bought 4*3=<<4*3=12>>12 pints
On Tuesday she bought 12/3=<<12/3=4>>4 pints
Before she returned any she had 4+12+4=<<4+12+4=20>>20 pints
She returned 4/2=<<4/2=2>>2 pints
After returning she had 20-2=<<20-2=18>>18 pints
#### 18