Zhang Liang has five sweets, and Liu Lan has 19 sweets. How much candy did Liu Lan give Sean? Liu Lan has twice as many sweets as Sean.
Answer: If Liu Lan gives Sean X candy, Liu Lan has twice as much candy as Sean.
19-x=(5+x)×2
19-x= 10+2x
2x+x= 19- 10
3x=9
x=9÷3
x=3
Liu Lan gave Sean three sweets, and Liu Lan had twice as many sweets as Sean.