Which expression is equivalent to 7(k^2) where k is an even number?

Me because some of question i don’t understand

Write numerical coefficient of y² in the expression 2x² - 15xy – 7y²

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).