I am having trouble finding out the correct equation.

Question

Chris is four years older than Belle. Doug is five years younger than twice Belle's age. The sum of their ages is 47. How old is each child?

Answer 1

Let d = Doug, c = Chris, and b = Belle.

Here's what we know:

c = b + 4 (Chris is 4 years older than Belle)

d = 2b - 5 (Doug is 5 years younger than twice Belle's age)

b + c + d = 47 (their total age is 47)

 

We have variable vales, so let's plug them in:

b + (b + 4) + (2b - 5) = 47

Simplify:

4b - 1 = 47

Add 1 to both sides:

4b = 48

Divide by 4:

b = 12

 

You can find c and d from here, and check the work.

Answer 2

Hello Gabby

 

C = Chris, B = Belle and D = Doug

 

Equation 1:

C = B + 4

Equation 2:

D = 2B - 5

 

Equation 3:

B + C + D = 47

 

Substitute equations 1 and 2 into 3,

 

B + (B + 4) + (2B - 5) = 47

 

4B - 1 = 47

 

4B = 48

 

B =  48 / 4 = 12

 

Belle is 12 years old.

 

Chris is 4 years older than Belle or 12 + 4 = 16 years.

 

Doug is 5 years younger than twice Belle's or (2 x 12) - 5 = 24 - 5 = 19 years

 

To confirm, B + C + D = 47

 

12 + 16 + 19 = 47