Using compatible numbers to estimate 83+34

 80 + 30
then add
80 + 30=110
then add the numbers you left out
3+ 4 = 7
and you get 117

or you can round up
90 + 40
90 + 40=130
then you subtract the numbers you added on
90 - 83 = 7
40 - 34 = 6
then you add those and subtract from 130 and you get 11Answer here

Idon’t know actually is more difficult