Question 114574
PERIMETER OF A TRIANGLE=SIDE1+SIDE2+SIDE3
LET X=THE FIRST SIDE.
THE SECOND SIDE=X-2
THE THIRD SIDE=X+12 
73=X+X-2+X+12
73=3X+10
3X=73-10
3X=63
X=63/3
X=21 FOR THE FIRST SIDE.
21-2=19 FOR THE SECOND.
21+12=33 FOR THE THIRD.
PROOF:
21+19+33=73
73=73