First, find the price of the sandwiches $5 per sandwich * 18 sandwiches = $<<5*18=90>>90.
Now add in the delivery fee $90 + $20 = $<<90+20=110>>110.
Now the tip $110 * 0.10 = $<<110*0.10=11>>11.
Add the tip to the price of the sandwiches $110 + $11 = $<<110+11=121>>121 in total.
#### 121