Question

Dad is 4 times as old as his son Jim. In 10 years, Dad's age will be 20 years more than twice Jim's age. How old is Jim?

If D = dad's age now and J = Jim's age now, which of the following systems could be used to solve the problem?


D = 4J and D + 10 = 2J + 20
D = 4J and D + 10 = 2(4J + 10) + 20
D = 4J and D + 10 = 2(J + 10) + 20

A?

Answer 1

Right now, let Jim's age = x
So, Dad's age is 4x


In ten years from now, Jim's age: x + 10
Dad's age is 4x + 10

So according to the problem, in 10 years, 4x + 10 = 2(x+10) + 20

Answer 2

I would use B:
D = 4J and D + 10 = 2(4J + 10) + 20