Question: Tim decides to light off some fireworks for the fourth of July.  He buys a package of fireworks worth $400 and another pack worth twice that much.  He gets a 20% discount on them.  He also buys a finale firework that costs $150.  How much did he spend in total?
Answer: 
The second package was worth 400*2=$800
So the two packages were worth 400+800=$1200
That means he got a discount of 1200*.2=$240
So the packages cost 1200-240=$960
So he spent a total of 960+150=$1110