PLEASE HELP THE WORK IS ABOVE

For what values of b will f(x)= logbx be a decreasing function? (16 )

Mustafa contributes 11% of his $67,200 annual salary to his 401k plan. what is his pretax income

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).