Aused boat dealership buys a boat for $2990 and sells it for $4200. what is percent increase?

It is a 40.5% increase, how I got my answer.

It is really simple, all I done was added $2,990 and on a caculater started at 100% increase would be 5,980, the reason I started out with 100% is because it is much easyer to judge how much I need to go down or up in percentage, so I knew that I needed to find $4,200, so I moved it down to 45% which equaled $4,335.5 so I brought it down to 41% which equals $4,215.9, so I brought it down to 40% which equals $4,186, then I brought it up to 40.5% which equals $4,200.95, but the .95 does not matter.

I hope this helps!