Answer :
Based on the sum of their ages, Mark's brother is 14 years old.
Let us assume the age of Mark be x. Now forming the equation based on mentioned information.
Mark's age = x
Mark's brother's age = x + 5
x + x + 5 = 23
Performing addition on Left Hand Side of the equation
2x + 5 = 23
Shifting 5 to Right Hand Side of the equation
2x = 23 - 5
Performing subtraction on Right Hand Side of the equation
2x = 18
Shifting 2 to Right Hand Side of the equation
x = 18a1 ÷ 2
Performing division on Right Hand Side of the equation
x = 9
So, Mark's age = 9
Mark's brother's age = 9 + 5
Mark's brother's age = 14
Hence, Mark's brother's age is 14 years.
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