The question is:
Choose the letter of the best estimate.

260 divided by 3

a. 60
b. 70
c. 90
d. 100

I think it is 100. Let me know if I am right. thank you,
Andrew

Here is one approach:

If 260 divided by 3 is some number then 3 times that number is 260. Thus try 3 times the possible answers.

a. 60x3=180
b. 70x3=210
c. 90x3=270
d. 100x3=300

Compare these answers to 260

a. and b. are too small

c. and d. are too big

(in fact, d. 100 is much too big and so is not correct)

270 is the closest to 260 so the answer is c. 90

In reality when I did this problem I ignored the zeros in 260, 60, 70 etc. so I looked at

a. 6x3=18
b. 7x3=21
c. 9x3=27
d. 10x3=30

and reached the same conclusion.