Start with Ethan being twice as old as his brother Adrian. If Adrian's age is represented by x, then we can use the expression 2x. Ethan is also three years older than twice that age though, so modify the expression to add three years.
2x + 3. Now substitute Adrian's age, 6, into x and solve.
2(6) + 3
12 + 3
15.
If Adrian is 6, then Ethan is 15.
