If a(x) and b(x) are linear functions with one variable which expression produces a quadratic function

In the diagram, the measure of angle 9 is 85° which angle must also measure 85°?

Amerchant has coffee worth $60 a pound that she wishes to mix with 50 pounds of coffee worth $90 a pound to get a mixture that she will sell for $70 a pound. how many pounds of the & 60 coffee should be used?

Tom drove 206 miles in 3.9 hours. estimate his average speed.