Jīnnián xiāoshòu'é zēngzhǎng le bǎi fēn zhī shíwǔ.
Sales grew fifteen percent this year.
Tips
grammar
Chinese percentages are written 百分之 N (literally 'of one hundred parts, N'), with the percentage following 之. So 50% = 百分之五十. The order is the reverse of English '15 percent'.