Thomas = x Huilan = x -15 (15 years younger than Thomas' age) If Huilan (x) + Thomas' age (x-15) equals 33, then ; x+x -15= 33 2x -15 =33 (do anything (throw -15 to the other side and then divide by 2) to leave x alone)
2x= 33+15
2x = 48 x = 24 Thomas is 24 and Huilan is 24-15 = 9 years old.