suppose the depth of the diver is d at time time t, rate is given by r=12 1/3 ft/ min. The equation representing the depth of the diver at time t will be:
f(t)=200-(12 1/3)t
Therefore the depth of the diver after t=4.5 min will be:
f(4.5)=200-(12 1/3)*4.5
f(4.5)=200-55.5
f(4.5)=144.5 ft
This means that after 4.5 minutes the diver will be 144.5 ft deep.
