Algebra 2 - need help (photo)

Solve 2x+y=3 x+y=5 in substitution method

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).

Express the following as a function of a single angle. cos(60) cos(-20) - sin(60) sin(-20)