Answer:
$75.
Step-by-step explanation:
We have been given that Grammy gave the server a $15 tip. The tip was 20% of the cost of dinner.
Let x be the cost of Grammy's dinner. We need to find x such that 20% of x equals to 15. We can represent this information as:
[tex]\frac{20}{100}x=15[/tex]
[tex]0.20 x=15[/tex]
[tex]x=\frac{15}{0.20}[/tex]
[tex]x=75[/tex]
Therefore, the cost of Grammy's dinner was $75.
