The ages of the brother and sister as obtained from the equations are :
- Brother, b = 10 years
- Brother, b = 10 years Sister, s = 20 years
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)
- (3 times sisters age) - (4 times brothers age) = 20
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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