Given the following system, what would be the best way to start solving the system? x+y=20
x=3y
(1 point)
A Solve for y in the second equation, and substitute x3 for y in the first equation.
B Solve for y in the first equation, and substitute the solution for y in the second equation.
C Substitute 3y from the second equation for x in the first equation.
D Solve for x in the first equation, and substitute the solution for x in the second equation.
I think D (please explain why don't just give the answer)

This race was first held in 1953 on august 16th. every decade the race finishes with a festival. how many years is this?

Four airplanes carrying a total of 400 passengersarrive at the detroit airport. the airplanes carry, respectively,50, 80, 110, and 160 passengers.a) one of the 400 passengers is selected uniformly at random.let x denote the number of passengers that were on theairplane carrying the randomly selected passenger. find var(x)for x as given in the problemb) one of the 4 airplane drivers is also selected uniformly atrandom. let y denote the number of passengers on the chosen driver’s airplane. find var(y) for y as given in the problem

If f(x) = x+8 and g(x) = 4x- 3, find (f+g)(x)