The second grade of primary school is estimated to be 38 + 16 18 + 21 + 27 98_ 51+16

Estimated, 38 can be regarded as 40, 16 as 15, and then 40 + 15 = 55
18 can be regarded as 20, 21 as 20, 27 as 30, and then 20 + 20 + 30 = 70
The 98_ What does this mean, subtraction? If it does, it's fine
98 can be regarded as 100, 51 as 50, 16 as 15, and then 100-50 + 15 = 65
For reference only

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