Answer:
Lucie is 8 and her brother is 13
Explanation:
Lucie is 5 years younger than her brother. Three years ago, Lucie was twice younger than her brother.
Let L be the Lucie age
and B be the brothers age
Lucie is 5 years younger than her brother
L= B-5
Three years ago, Lucie age is L-3
brother is B-3
Lucie was twice younger than her brother.
2(L-3)= B-3
Plug in B-5 for L
2(B-5-3)= B-3
2B - 16= B-3
Subtract B from both sides
B - 16 = -3
Add 16 on both sides
B= 13
Age of brother = 13
Age of Lucie = brother -5 = 13-5 = 8