As per linear equation, the photo frame's diameter is 18 cm.
What is a linear equation?
"A linear equation is an equation in which the highest power of the variable is always 1. It is also known as a one-degree equation."
Given, the radius of the photo frame is 9 cm.
Therefore, the photo frame's diameter is
[tex]= 2(radius)\\= 2(9) cm\\= 18 cm[/tex]
Learn more about a linear equation here: https://brainly.com/question/21440319
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