Robert is thinking that his father is 7 years more than twice his own age, and his grand father is 4 years less than twice his father’s age. If Robert’s grandfather is 70 years of age, how old is Robert?
The fathers age = F Roberts age = R Grandfathers age = G
The fathers age can be represented by: F = 7 + 2R The Grandfathers age can be represented by: G = 2F - 4 Since the grandfathers age is 70, plug that in for G and solve the equation: 70 = 2F - 4 (add 4 to both sides) 74 = 2F (divide both sides by 4) 37 = F Now that we have the fathers age, substitute it for the above equation 37 = 7 + 2R (subtract both sides by 7) 30 = 2R (divide both sides by 2) 15 = R
