SOLUTION: Lucas is 9 years older than three times his son’s age. In 14 years, the age of Lucas will be 6 years more than twice his son’s age. Find their present ages.
L = 3y + 9 (1)
L+14 = 2*(y+14) + 6. (2)
Substitute (1) into (2). You will get
(3y + 9) + 14 = 2*(y+14) + 6
3y + 23 = 2y + 28 + 6
y = 28 + 6 - 23 = 11.
Answer. The son is 11 years old. The father (=Lucas) is 3*11 + 9 = 42 years old.