We have a question: Emma got $2000 from the bank. She bought $400 of furniture and gave 3/4 of the rest to her friend Anna. How much is left with Emma?
And an answer: 400
So how you got the answer?
Emma had $2000 - $400 = $1600 left after buying furniture. Emma gave Anna 3 / 4 * $1600 = $1200. So, Emma is left with $1600 - $1200 = $400.

We have a question: If farmer Steven can use his tractor to plow up to 10 acres of farmland per day, or use the same tractor to mow up to 12 acres of grassland per day, how long would it take him to plow his 55 acres of farmland and mow his 30 acres of grassland?
And an answer: 8
So how you got the answer?
At a rate of 10 acres per day, he can plow his 55 acres of farmland in 55 / 10 = 5.5 days. At a rate of 12 acres per day, he can mow his 30 acres of grassland in 30 / 12 = 2.5 days. Altogether, it would take him 5.5 + 2.5 = 8 days to completely mow and plow his land.

We have a question: The Reptile House at the zoo has 5 fewer animals than 3 times the number of animals housed in the Rain Forest exhibit. If the Reptile House has 16 animals, how many are in the Rain Forest exhibit?
And an answer: 7
So how you got the answer?
Let x be the number of animals in the Rain Forest exhibit. 3x - 5 = 16. 3x = 21. x = 7.