Here is a tip-
If the question says "about how many" or "about how much" they are usually asking for an estimate.
The first Question-
$989.99 can be rounded to $1,000. $311.25 can be rounded to $300. $1,000-$300=$700. They need about $700.
The second question-
If 185 people visited on Friday, and Saturday had twice as many, 185*2=370. If there were 370 people on Saturday, and 50 less people came on Sunday, 370-50=320. Now combine all three days, 185+370+320=875 people.
The third question-
If Tomás's meal costs $7.89, we can round to $8. Lisa's cost of $9.05 can be rounded to $9. $9+$8=$17.
So their meal costs about $17.
