The easiest way to find the answer is to convert all of the units into inches and solve it with basic addition. We know that 1 foot equals 12 inches and that 1 yard equals 36 inches. With this in mind, we know the first board is 34 inches long, and the second board is 57 inches long. Now we can just add these together, which yields a result of 91 inches long. To simplify this, we need to start by dividing by 36. Solving that gives us 2, so we know that we have 2 yards. It also leaves 19 inches left over. We can now divide that by 12 to calculate how many feet there are. This shows us we have 1 foot with 7 inches left over.
To summarize, the length of the boards put together is 2 yards, 1 foot, and 7 inches, or 91 inches.