A) Let t represent the number of tickets Erica bought. The the equation describing her rebates can be written as
... 3t + 0.80×15 = 18
B) Here's the solution to the equation.
... 3t + 12 = 18 . . . . . . simplify; rules of arithmetic
... 3t = 6 . . . . . . . . . . .subtract 12; subtraction property of equality
... t = 2 . . . . . . . . . . . . divde by 3; division property of equality
C) Erica bougth 2 movie tickets last month.