In seven years, huang will be two times as old as he was last year. how old is he now?

Let H be Huang's age.  Translating the sentence to an equation gives
H+7=2(H-1)
That is: in 7 years, when Huang's age is 7 more than it is now, his age will be 2 times what it was last year (when it was one less than it is now, or H-1)
Solving for H:
H+7=2H-2
H+7-2H+2=0
-H+-7-2=0
-H=-9
H=9
Now let's check:  In 7 years he will be 9+7=16
Last year he was 8 and 16 is indeed twice this age

All except for b, because polynomial functions can be quadratic, cubic, witticisms and etc only non negative exponents of negative it is not a polynomial function

i believe your answer is b.

good luck!

cutie~