(. i screenshot the question)
the polygons are similar, but not necessarily drawn to scale. find the value of x.
a. x=13
b. x=7
c. x=5.5
d. x=10

Ok so similar means corsponding sides are in the same ratio
8:2
16:4
x-3:2.5
it seems that the left side is 4 times the right so
since 8:2, 8=2 times4
therefor
x-3=4 times 2.5
x-3=10
add 3 to both sides
x=13

answer is A. x=13

Element 17 is chlorine it is a group 7 element(halogen) and belongs to period 3 of the periodic table