Answer: 6
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Step-by-step explanation:
The triangles are similar triangles (we can use the AA similarity theorem to prove this). So the vertical sides pair up, and the horizontal sides pair up, to form the proportion below
x/4.5 = 8/6
Note the order of the terms. I'm dividing the upper triangle's sides by the corresponding lower triangle's sides. Cross multiply and solve for x
x/4.5 = 8/6
6x = 4.5*8
6x = 36
x = 36/6
x = 6