Debbieis one year older than dave. james is twice as old as dave. joelle is twice as old as debbie. altogether their ages total 33. find each persons age. (let x = daves age)

X = dave's age
d = debbie's age
j = joelle's age

x + d + j = 33
d = x + 1
j = 2dj = 2(x + 1)

x + (x + 1) + 2(x + 1) = 33
x + x + 1 + 2x + 2 = 33
4x + 3 = 33
4x = 33 - 3
4x = 30
x = 30/4
x = 7.5 <=== dave is 7.5 (or 7 1/2) years old

d = x + 1
d = 7.5 + 1
d = 8.5 <=== debbie is 8.5 (or 8 1/2) years old

j = 2(x + 1)
j = 2(7.5 + 1)
j = 2(8.5)
j = 17 <=== joelle is 17 years old