Let x be the number for Debra.
Write equation as you read the problem
Debra + Brian + Austin = 87
x + (x+7) + 2x = 87
Simplify and solve
4x = 87 - 7 = 80
x = 80/4 = 20.
ANSWER. Debra 20; Brian 20+7 = 27; Austin 2*20 = 40.