How do I estimate 0.509375

If f(x)=2x-6 and g(x)=3x+9, find (f-g)(x)

When steve woke up. his temperature was 102 degrees f. two hours later it was 3 degrees lower. what was his temperature then?

Which ordered pair is the best estimate for the solution of the system of equations? the graph of the system of equations : y = 3/2x +6 and y=1/4x - 2 , -3) .5, -3.5) , -4) , -3.5)