Using your answers from parts b and c, what are the ages of the brother and sister, respectively?

The ages of the brother and sister as obtained from the equations are :

The complete version of the question is attached below :

Given that :

The sum of the ages of the brother and sister = 30

Let :

Age of brother = b

Age of sister = s

Mathematically,

b + s = 30 - - - (1)

Mathematically,

3s - 4b = 20 - - - (2)

Using both equations, we can obtain the values of b and s

From (1)

Isolating s ;

s = 30 - b - - - (3)

Put (3) as s in (2) ;

3(30 - b) - 4b = 20

90 - 3b - 4b = 20

- 7b = 20 - 90

-7b = - 70

b = 10

From (1):

b + s = 30

10 + s = 30

s = 30 - 10

s = 20

Hence, b = 10 ; s = 20

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