Answer:
13.5x + 5
Explanation:
12x + 1.5x - 2 - 7 (you always want to work left to right)
13.5x - (2 - 7) (you are free to use the associative property here to isolate like terms)
13.5x - (-5) (remember a number less in value subtracted from a higher value will result in a negative value; giving you this value for instance.)
13.5x + 5 (now since it was basically subtracting a negative from 13.5x you can technically say the same thing by turning the negative value to a positive however you must do the opposite of subtraction as well.)