Answer:
10a + 2b
Step-by-step explanation:
Add the lengths of all sides:
3a + b + b + 2a - b + 3a + b + b + 2a - b
Now combine like terms:
10a + 2b
1/15 as a decimal would be 0.6666666......
Or you can round that off to 0.67
Answer:
Brand b has a better unit price.
I assume you mean 
, and not 
, since this doesn't satisfy the ODE.
Assume a second solution of the form 
, where 
is a function of 
. Then
Substituting into the ODE gives
where we omit the second term because it's already accounted for by 
.
