Question 31515
Let the shortest side be x feet long
The length of the second side = 2x
The length of the third side = x+3

Perimeter is the sum of all three sides
Thus, x+2x+(x+3) = 19
=>4x+3 = 19
=>4x = 16
=>x = 4

The sides of the triangle are 4 feet, 8 feet(=2*4), and 7 feet(=4+3) long.