Which relationship has a zero slope?

What is the celsius temperature that is equal to 94 degrees fahrenheit using the formula f=9/5 c+32

Which of the binomials below is a factor of this trinominal? x^2-13+30

The u-drive rent-a-truck company plans to spend $13 million on 320 new vehicles. each commercial van will cost $25 comma 000, each small truck $50 comma 000, and each large truck  $80 comma 000. past experience shows that they need twice as many vans as small trucks. how many of each type of vehicle can they buy?