Answer:
x = 6
Step-by-step explanation:
Since the triangles are similar then the ratios of corresponding sides are in proportion, that is
[tex]\frac{DE}{XY}[/tex] = [tex]\frac{EF}{YZ}[/tex] , substitute values
[tex]\frac{10}{x-1}[/tex] = [tex]\frac{8}{4}[/tex] = 2 ( multiply both sides by x - 1 )
2(x - 1) = 10 ( divide both sides by 2 )
x - 1 = 5 ( add 1 to both sides )
x = 6
