Carcass wrote:
Sarah is twice as old as her youngest brother. If the difference between their ages is 15 years. How old is her youngest brother?
A. 10
B. 15
C. 20
D. 25
E. 30
We can solve this question using one variable or two variables. Let's use one variable.
We want to find the age of the youngest brother.
So, let x = the age of the youngest brother
This means 2x = Sarah's age (since she is twice as old as her youngest brother)
The difference between their ages is 15 yearsIn other words: (Sarah's age) - (the youngest brother's age) = 15
Substitute to get: 2x - x = 15
Simplify: x = 15
So the youngest brother is 15 years old.
Answer: B