X - y = 4 and x + y = 9

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).

Write the expression 7x^3-28xy^2 as the product of 3 factors

Using only the digits 5, 6, 7, 8, how many different three digit numbers can be formed if no digit is repeated in a number?