If Luke is 20, he will be 20+8 = <<20+8=28>>28 years old in eight years.
In eight years, Mr. Bernard will be 3 times as old as Luke is now, a total of 3*20= <<3*20=60>>60 years old.
Mr. Bernard is now 60-8= <<60-8=52>>52 years old
The sum of their current ages is 52+20 = <<52+20=72>>72
Their average age is 72/2 =<<72/2=36>>36
10 less than their average age is 36-10 = <<36-10=26>>26 years.
#### 26