The answers are 901 and 518.
In order to find out these answers, you first figure out whether you are adding or subtracting. Take the first one for example: ____ + 349 = 1250. You are adding. So what you can do is do the opposite, which is subtract in this instance, and put the numbers in order with the number after the equal sign first. That's how I ended up with 901.
Now with the other problem, its not as simple. We have to subtract 347 from 865.
Hope this helps :)