Y=9
Since we are talking about perimeter add all of the sides together and set them equal to the total creating the equation 68=3y+y-1+4y-3. Combine like terms and you get 68=8y-4. From here you can use inverse operations to solve for the value of y. So add 4 to both sides and you get 72=8y (-4 and +4 cancel out). Finally divide both sides by 8 and you are left with 9=y.
Always double check your work:
3(9)+(9)-1+4(9)-3=68
27+8+33=68
68=68