No links or weird answers, please :(
Are all of these graphs functions? Explain why or why not.

Bob the builder is making 480kg of cement mix. this is made by cement, sand and gravel in the ratio 1: 3: 4

Melissa is purchasing a $160,000 home and her bank is offering her a 30-year mortgage at a 4.9% interest rate. in order to lower her monthly payment, melissa will make a 20% down payment and will purchase 3 points. what will her monthly mortgage payment be? a. $645.98 b. $650.46 c. $662.93 d. $606.69

Solve the system of equations. 2x-2y=-4 and x+y=8. show work