first, the estimating part. by estimation, you can see, like the problem says, how reasonable your answer is. In this instance, 1035 is close to 1000, and 1000 times 6 is 6000. we should get an answer in this range, and if we don't, we know something's up.
now, to actually solve it
1035 per week* 6 weeks= 1035*6=6210.
It is in the range of 6000, so we can see its reasonable, and a double check ensures it is correct