so it would be 2w-5 for the width equation. to find both sides of the width you do 2(2w-5) which gives you 4w-5. from there you write your equation to solve for w.
Equation: 4w-5= 34 (its 34 because its half of 68) w=11
To find l you multiply 11 by 2 then subtract that from 68 which gives you 46. then you divide that by 2 which gives you 23
l=23