Answer:
Liams Dinner Bill before tip=$15.65
Step-by-step explanation:
Total amount Anthony paid=Anthony's Bill+Anthony's Tip
where;
Anthony's Bill=$15
Anthony's Tip=20% of $15=(20/100)×15=$3
Replacing;
Total amount paid by Anthony=(15+3)=$18
Total amount paid by Liam=Liam's Bill+Liam's Tip
where;
Liam's Bill=B
Liam's Tip=15% of B=(15/100)×B=0.15B
Replacing;
Total amount paid by Liam=(B+0.15B)=1.15B
Total amount paid by Anthony=Total amount paid by Liam
18=1.15B
B=(18/1.15)=$15.65
Liams Dinner Bill before tip=B=$15.65