Shelby and her mom made 12 bags of buttered popcorn + 10 bags of caramel popcorn = <<12+10=22>>22 bags.
Of those 22 bags, her brother took 3 bags of buttered popcorn + 1 bag of caramel popcorn = <<3+1=4>>4 bags.
So now Shelby has 22 bags – 4 bags = <<22-4=18>>18 bags of popcorn left.
#### 18