The answer is B. The values of y must only be positive because it is equal to

The other options states that the values of y could be negative which is why it is wrong.
since triangles are similar
4/x = 7x/7
=》 4/x = x
=》x^2 = 4
=》 x = 2
for right triangles a^2 = b^2+c^2
DF^2 = 7^2+2^2 = 53
=》 DF = 7.28
perimeter of DEF = 7 +2+7.28 = 16.28
Answer:
3.2
Step-by-step explanation: