Answer: 5
Step-by-step explanation:
Since [tex]\overline{GH} \parallel \overline{DE}[/tex], by the corresponding angles theorem, [tex]\angle FGH \cong \angle FDE, \angle FHG \cong \angle FED[/tex]. This means [tex]\triangle FGH \sim \triangle FDE[/tex] by AA.
As corresponding sides of similar triangles are proportional,
[tex]\frac{10}{x+3}=\frac{10+x}{12}\\(10)(12)=(10+x)(x+3)\\120=x^{2}+13x+30\\x^{2}+13x-90=0\\(x+18)(x-5)=0\\x=-18, 5[/tex]
However, as distance must be positive, we consider the positive solution, x=5.
Therefore, the answer is 5
