You don't need to estimate - it is an easy enough sum: 136.
47 plus 61 is equal to 108.
16 + 12 + 47 = 75
47 plus 39 gives 86.
63 plus 47 plus 42 plus 21 is equal to 173.
75+2(32)+4(39)+47 =75+64+156+47 =75+220+47 =122+220 =342
You can tell by looking at it that 47 + 84 is 131. I suppose you could estimate 50 + 80 or 45 + 85
57+97+37+47+6 = 244
15 + 47 = 62
94 + 47 = 141
45 + 47 = 92
114 + 47 = 161
47 + 5 = 52