natalie budgets $150 for yoga training but doesn’t want to spend all of that money. She buys a yoga mat for $10 and spends $9 per day on yoga classes. Which inequality represents the number of day,d, that Natalie can take classes and stay under (less than) her budget?

All you have to do is round the numbers and then divide. For example, here are the first 2 answers.

b. 2,000 divided by 20 = 100
c. 8,000 divided by 40 = 200

So if you had 3,861, you would round that to 4,000, and round 59 to 60.
So basically, in the 100's, if it is 0-4, round down. (Ex. 4,371=4,000), and if it is 5-9, round up. (Ex. 7,920=8,000), then just divide the two numbers.