Help me please or I fail this year

The amount of energy it takes to lift a box might be a function of which of the following

Each month, a shopkeeper spends 5x + 14 dollars on rent and electricity. if he spends 3x−5 dollars on rent, how much does he spend on electricity? for which value(s) of x is the amount the shopkeeper spends on electricity less than $100? explain how you found the value(s).

Which expression is not a polynomial?