Triangle ABC is similar to triangle DEF. So, the length of the side EF is 15 cm and this can be determined by using the properties of similar triangle.
Given :
It is given that the triangle ABC and triangle DEF are similar. Therefore, the ratios of corresponding sides are also equal.
[tex]\rm \dfrac{AC}{DF} = \dfrac{BC}{EF}[/tex]
Now, substitute the values of AC, DF, and BC in the above equation.
[tex]\rm \dfrac{12}{10} =\dfrac{18}{EF}[/tex]
[tex]\rm FE = \dfrac{10\times 18}{12}[/tex]
EF = 15 cm.
So, the length of the side EF is 15 cm.
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https://brainly.com/question/10652623