If there are 8 marbles in a group , and 5 out of every 8 is red, than in six groups there would be 5, 10, 15, 20, 25, 30 red marbles.
This lists the group of 6 sets.
30 red marbles in 6 sets.
In 2 2/3 months you ran 76 miles.
To know how many miles you ran each month, you can simply use cross multiplication as follows:
number of miles per month= (76) / (2 2/3)
= 28.5 miles
DI/dx=-850x+45500
d2l/d2x=-850 so when dl/dx=0 it is an absolute maximum for l(x)...
dl/dx=0 only when:
850x=45500
x=53.53
x=54 years of age (rounded)