Alex rents a car for one day. The charge is $18 plus $0.12 per mile. Alex wants to spend exactly $30. Write an equation to represent the situation.
A) 30 - 0.12 = 18x
B) 18 + 0.12x = 30
C) 18 - 0.12x = 30
D) 18x + 0.12 = 30
please help​