Answer:
(800 x 9) + (10 x 9)
Step-by-step explanation:
Find out what 810 x 9 is:
810 x 9 = 7290
Then see which expression has the same answer. Personally I'd check all of them, but luckily the first expression is the correct one so you don't need to go through the rest (since it only asks for one correct expression):
(800 x 9) = 7200
(10 x 9) = 90
7200 + 90 = 7290
