Yvette spent 7.50+10+8.5+9 = $<<7.50+10+8.5+9=35.00>>35.00 on ice cream sundaes
Her bill comes to $35.00 and she leaves a 20% tip for the waiter so that's 35*.20 = $7.00
The bill was $35.00 and she added a $7.00 tip for a total of 35+7 = $<<35+7=42.00>>42.00
#### 42