Which polynomial represents the sum below?

Answer:
option B
Step-by-step explanation:
We have:
3x^2+7x+3 and 5x^2+12x
where
a=3x^2+7x+3
b=5x^2+12x
a+b=3x^2+7x+3 +5x^2+12x
we sum each term:
3x^2+5x^2=8x^2
7x+12x=19x
3+0=3
so we have: a+b= 8x^2+19x+3
finally we have
8x^2+19x+3= option B