The square of (-abc) is

How do you use the additive inverse to evaluate an expression that uses subtraction in a full sentence

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).

What’s the answer? and how do i solve it ?