Answer:
4.5 cm
Step-by-step explanation:
Givens: 20 mm, 17 mm and 8 mm
Operations: Addition and Division
Solutions: 20 + 17 + 8 = 45 mm
45 mm ÷ 10 = 4.5 cm
Answer: 4.5 cm
[tex]\tt{ \green{P} \orange{s} \red{y} \blue{x} \pink{c} \purple{h} \green{i} e}[/tex]