I don't understand how to "estimate the range". The question is...
Estimate a range for each sum.
7.8+31.39+6.95
I could say
7 + 31 + 6 = 44 low
or
8 + 32 + 7 = 47 high
but that would be kind of silly
and I would be more likely to estimate using nearest whole numbers
8 + 31 + 7 = 46