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