What is this plzz need for math homework it is very hard

I believe the correct answer is “a5+2” or, like the question says to write it, “7 L(centimeters.)” this is because using the normal steps for equations, you add up how many “a”s you have total. Then you combine “-1 and +3”, which gives you positive 2. Then you add 5+2 which gives you 7. Hope this helped! :) please mark as Brainliest if the answer is correct!