Answer:
Shawn's age = 5 years
Ash's age = 8 years
Crystal's age = 20 years
Oscar's age = 16 years
Explanations:
Let Ash's age be represented by A
Let the Shawn's age be represented as S
Let the Crystal's age be represented as C
Let Oscar's age be represented as O
Ash is three years older than Shawn
A = S + 3.....................(1)
Crystal is 4 times as old as Shawn
C = 4S................................(2)
Oscar is twice as old as Ash
O = 2A.................................(3)
Altogether, their ages total 49
A + S + C + O = 49 ...............(4)
First, to get Oscar's age in terms of Shawn's age, substitute equation (1) into equation (3)
O = 2 ( S + 3)
O = 2S + 6..................(5)
Substitute equations (1), (2), and (5) into equation (4)
(S + 3) + S + (4S) + (2S + 6) = 49
S + S + 4S + 2S + 3 + 6 = 49
8S + 9 = 49
8S = 49 - 9
8S = 40
S = 40 / 8
S = 5
Shawn's age = 5 years
To get Ash's age, substitute the value of S into equation (1)
A = S + 3
A = 5 + 3
A = 8
Ash's age = 8 years
To get Crystal's age, substitute the value of S into equation (2)
C = 4S
C = 4(5)
C = 20
Crystal's age = 20 years
To get Oscar's age, substitute the value of A into equation (3)
O = 2A
O = 2(8)
O = 16
Oscar's age = 16 years