Respuesta :
Answer:
d) 4.
Step-by-step explanation:
Let Santiago be x years old today.
Then Juan is x + 8 years old.
In 4 years Santiago will be x + 4 years.
In 4 years Juan will be x + 12 years.
From the given information:
x + 4 = 0.5(x + 12)
x = 0.5x + 6 - 4
0.5x = 2
x = 2 / 0.5
x = 4.
Let S be Santiago’s age
Let J be Juan’s age.
Since Santiago is 8 yrs younger than Juan, we can write
Equation 1: S = J-8
In 4 yrs, Santiago age will be S + 4,
In 4 yrs, Juan’s age will be J + 4.
Given:
In 4 yrs, Santiago will be half of Juan’s age, so ..
Equation 2: S+4=(J+4)/2
We know the value of S from equation 1. Substitute S=J-8 in equation 2, we get
J -8 + 4=(J+4 )/2
J-4 = (J+4 )/2
2( J- 4) =J + 4
2J-8 =J + 4
2J-J =8+ 4
J = 12
Substitute J= 12 in equation 1
S= 12-8
S = 4
So, Santiago’s age is 4 yrs today.
Let J be Juan’s age.
Since Santiago is 8 yrs younger than Juan, we can write
Equation 1: S = J-8
In 4 yrs, Santiago age will be S + 4,
In 4 yrs, Juan’s age will be J + 4.
Given:
In 4 yrs, Santiago will be half of Juan’s age, so ..
Equation 2: S+4=(J+4)/2
We know the value of S from equation 1. Substitute S=J-8 in equation 2, we get
J -8 + 4=(J+4 )/2
J-4 = (J+4 )/2
2( J- 4) =J + 4
2J-8 =J + 4
2J-J =8+ 4
J = 12
Substitute J= 12 in equation 1
S= 12-8
S = 4
So, Santiago’s age is 4 yrs today.
