Ava's Height = [tex]a[/tex]
Olivia's Height = [tex]o[/tex]
Lucas' Height = [tex]l[/tex]
We know from the question that;
[tex]o = \frac{1}{2}l[/tex]
If Lucas is 1.78m tall, then he is 178cm tall, so [tex]l = 178[/tex]
[tex]o = \frac{1}{2}178[/tex]
[tex]o = 89[/tex]
We also know that;
[tex]a + 23 = o[/tex]
As we have worked out that [tex]o = 89[/tex],
[tex]a + 23 = 89[/tex]
[tex]a = 89 - 23[/tex]
[tex]a= 66[/tex]
[tex]\boxed {a = 66cm, o = 89cm}[/tex]
