Question 105716
Let's let x represent Richard's age.
Richard's age in 11 years, can then be represented as x + 11.
15 years ago, Richard's age would have been x - 15.
Finally, we know that Richard's age in 11 years (x + 11) will be three times what it was 15 years ago (3 * (x - 15)), and that forms an equation that looks like:

x + 11 = 3 * (x - 15)

Now to solve... 
x + 11 = 3(x - 15)  (problem restated)
x + 11 = 3x - 45    (right side expanded)
    11 = 2x - 45    (subtract x from both sides)
    56 = 2x         (add 45 to both sides)
    28 = x          (divide both sides by 2)

Richard is 28 years old.