Question 799622
Check which terms of the equation do not have L in them.  L only occurs to the first power (exponent 1), so you want all terms of L on one side, and all other terms on the other side; and then you have one or two further steps.


Solve for L:  {{{S=2WL+2LH+2WH}}}, as given.
Symmetric Property;
Additive Inverse of 2WH;
Reverse of Distributive Property to get a factor of L;
Multiplicative Inverse Property, for the binomial factor on L.


That is a list of properties to use.  Please try to manage the actual steps.