15 red marbles because 40 divided by 8 is 5. since the ratio from red to blue marbles is 3 to 8 this makes us have to multiply 5 x 3 because of how many times 8 goes into 40.
Step-by-step explanation: Terry descended 110 feet in the air so where was he before he descended? -110 feet 110 feet away from the cave so reverse that and hes 110 feet away :) hope this helps and is right.