Not sure if I did this right Can someone help? Find the value of x.

Answer:
6
Step-by-step explanation:
Given :
⇒ The triangles are similar
⇒ The sides are in proportion
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Solving :
⇒ [tex]\frac{6}{15+6} = \frac{8}{3x+10}[/tex]
⇒ [tex]\frac{6}{21}= \frac{8}{3x+10}[/tex]
⇒ [tex]\frac{2}{7} = \frac{8}{3x+10}[/tex]
⇒ [tex]\frac{1}{7}=\frac{4}{3x+10}[/tex]
⇒ 1(3x + 10) = 7(4)
⇒ 3x + 10 = 28
⇒ 3x = 18
⇒ x = 6
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Solution :
The value of x is 6