Me. kirk drove 164 miles in the morning and 219 miles in the afternoon. estimate the total number of miles she drove that day

There are multiple ways in which to come up with an answer here, depending upon the degree of accuracy you want in your estimate.

You could represent 164 by 160 and 219 by 220, to the nearest 10s place.
Then your estimate of the sum of 164 and 219 would be 160 + 220, or 380.

You could also round off 164 to 200 and 219 to 200.  The resultant sum would then be 400, which is close to 380.