Rounding to estimate - it's something that comes in handy if you're just after a rough answer, or to make sure your actual answer was in the right area. Estimate just means 'a good guess'. To round to estimate, you need to round both the numbers in the sum before you add them.
So here, to estimate 34 + 22, I'd round it to 30 + 20, the nearest tens, to get 50. The actual answer is 56, so it wasn't far off.
How do we round in the first place? We've have covered rounding before, but if you need a refresher have a look at the BBC Bitesize resource:
Log on to PurpleMash and you'll see Day 37 - Rounding To Estimate. Remember, you just need to pick which of the sums would get you a good estimate of the actual answer. Good luck!