$37.50
tax = 8%
tip = 18%
a) 37.5 ------------------ 100%
x ------------------- 8%
x = (8 x 37.5) / 100
x = 3
Tax = $3
b) Money of lunch plus tax = $40.5
40.5 -------------------- 100
x --------------------- 18
x = (18 x 40.5) / 100
x = 7.29
Total amount paid = 7.29 + 40.5
= $ 47.79