The total cost of the entrees is 4 * $20 = $<<4*20=80>>80.
The total cost of the dinner is $80 + $10 = $<<80+10=90>>90.
The tip is $90 * 0.20 = $<<90*0.20=18>>18
The total cost with tip is $90 + $18 = $<<90+18=108>>108
#### 108