Answer
32in, 16 in , 28 in
Work Step by Step
Lets take length of second side be x in
Length of third side be 12 more than the second side= x+12 in
Length of first side be twice of second side = 2x
Perimeter of triangle = length of first side + second side+ third side
76 = 2x + x+ x+12
76 = 4x + 12
4x = 76 - 12 = 64
x = $\frac{64}{4}$ = 16 in
Therefore Length of first side = 2x = 2*16 = 32in
Length of second side = 16in
length of third side = x+12 = 16 + 12 = 28in