Well, you’re starting out with 34 bales of hay. So, that’s your starting point. Then you end up with 64 so that’s your ending point. The setup would be
34 + X = 64
Now to figure out x, you would subtract 34 on both sides to get
X = 64 - 34
Then, after the subtraction you’d get:
X = 30
Understand that this means Dan added 30 more bales of hay into the barn.