It's been a long time, please be patient...(the answer [L>=160])
solve for L
U = 1 over 1 + 2 (80/L) >=.5
step 1 (Hopefully this first step is correct?)
.5 <= 1 over 1 + 160/L
step 2
.5 <= 1/1 + 1 over 160/L
step 3
.5 <= 1 + L/160
step 4 (I'm close but the ".5" is not part of the answer, why?)
160 <= .5 + L
solve for L
U = 1 over 1 + 2 (80/L) >=.5
step 1 (Hopefully this first step is correct?)
.5 <= 1 over 1 + 160/L
step 2
.5 <= 1/1 + 1 over 160/L
step 3
.5 <= 1 + L/160
step 4 (I'm close but the ".5" is not part of the answer, why?)
160 <= .5 + L