Question

Mrs. Chen has two brothers. Mark is 7 years older than Mrs. Chen and Eric is 11 years younger than Mrs. Chen. The sum of all three of their ages is 149. Use the 5-D Process to determine the age of Mrs. Chen. ​

Answer 1

Mrs. Chen is 51 years old.

Mark is 7 years older than Mrs. Chen.

Eric is 11 years younger than Mrs. Chen.

The sum of all three of their ages is 149.

Develop a plan: Let's use algebra to represent the ages of the three siblings.

Let x be Mrs. Chen's age.

Mark's age is 7 years older than Mrs. Chen, so it is x + 7.

Eric's age is 11 years younger than Mrs. Chen, so it is x - 11.

The sum of their ages is 149, so we can write an equation: x + (x+7) + (x-11) = 149

Draw a conclusion:

Simplifying the equation:

3x - 4 = 149

3x = 153

x = 51