Quickly please I have like 7 minutes of class

Which values for a and b will create infinitely many solutions for this system of equations? ax-y=8 2x+y=b

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).

Divide. write in simplest form 41/6 divided by 10