Need help with question 2., and number 3. plz it’s about functions

John bought 2 horses at rs 20000 each

What is the missing step in this proof ?

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?