Answer:
10
Step-by-step explanation:
(9 + 10+ 1/1 + 1(1) - 21 + 20) / 2
(9 + 10 + 1 + 1 -21 +20) /2
(21 - 21 + 20) /2
(20) / 2
Hope this helps
PLZ MARK BRAINLIEST