Answer:
x + 12 ≤ 20 x=8
Step-by-step explanation:
Since Larissa is able to use it up for 20 hours and she has been using it for 12 hours now so add 12 with 12 and 20 with 12 then subtract the sum from the added numbers and you will get 8
So Larissa has 8 hours left on her watch before it needs to charge