Answer:
158cm
Step-by-step explanation:
Martine had the height of 50cm when born.
Every year she grows at an average rate of 6cm
So the the first 18 years will be 6cm × 18 = 108cm
She will be 108cm + 50cm = 158cm tall by the time she turns 18 years
50cm + (6 × 18)cm
50cm + (6 × 18)cm50cm + 108cm
50cm + (6 × 18)cm50cm + 108cm158cm