You can put this solution on YOUR website! Let x be the number then adding 3 to the number we get x+3. Tripling it we get 3*(x+3). 17 more than the number is 17+x. As these are equal we get that
3*(3+x)=17+x
So
9+3*x=17+x
3*x-x+9-17=0
2*x-8=0
2*x=8
x=4