After isabella, maria takes 47 shells. how many shells are now left in the garcia family's collection

Well if there are 253 shells to begin with and Maria took 47 you would do 253-47 which equals 206 shells, because 47 are taken away from the original 253. But you'll also need to subtract the amount that Isabellla took as well. so 253-x, where x is the amount of shells isabella took