Answer:
3.1 x 10^9
Step-by-step explanation:
(2.8 x 10^9) + (3 x 10^8) = (28 x 10^8) + (3 x 10^8)
= (28+3) x 10^8
= 31 x 10^8
= 3.1 X 10^9
the length of BC is 9.
x=9
y parallel =10 or 10