Which of these is an equation?

a
9x - 7

b
(b + 7) x 3

c
4x + 9 = 45

d
(⅔)x - 3 > c

Sam is a waiter at a local restaurant where he earns wages of $5 per hour sam figures that he also eams about $3 in tips for each person he serves sam works 6 hours on a particular day. if n represents the number of people sam serves that day, which of the following functions could sam use to figure ehis total earings for the do o a. en) = 30 o b. en) = 5n+ 18