Me solve this linear equation! you if you do me! it means a lot : ))

Find the value of the cosine for angle a

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).

Using elimination, what is -4x+2y=-12 4x+8y=-24