The equation would be
(644-200)/12=x
The number of albums he sold would be
37
- explanation= If Floyd gets $200 a month plus $12 dollars for every album he sells this month he got 644. He gets $200 because its a new month so that 200 dollars wouldn't count so you subtract it from 644 and your left with 444 which you divide by 12 because each album is 12 dollars and you have to see how many albums ($12) fits in 444, that gets you to 37 so that means there's 37 albums he sold last month.