3. estimate:
6.8
+4.2
how come you did not estimate the problem

~11  (~ can be replaced with the word about or around)

If you were asking why one might not estimate this problem the answer is:

The values in this equation only include tenths which are not very difficult to add without rounding. While estimating can still be done, it is not necessary.

Step-by-step explanation:

When estimating, we start with rounding our numbers. In this case, we would be rounding to the nearest whole number.

6.8  ->   7     (8 is above 5 meaning we round up)

4.2  ->   4     (4 is below 5 meaning we round down)

This would leave us with the equation: 7 + 4 which equals 11.

~Hope this Helps!~