Jeremy's grandfather is four times as old as he is. If you add their ages together, you will get ninety. How old is Jeremy's grandfather? A. 18 B. 19 C. 70 D. 72

Let Jeremy's age be x

if Jeremy's grandfather is four times as old as he is, grandfather's age is 4x

if the sum of their ages is 90, we have

x%2B4x=90

5x=90

x=90%2F5

x=18->Jeremy's age

Jeremy's grandfather will be 4x=4%2A18=72

answer:

D. 72