Y=4x+3 equals what does this mean i don't understand

The perimeter of a movie screen is 54 meters. the screen is 18 meters wide. how tall is it?

Pyotr tchaikovsky sporting goods operates on a 45% overhead based on the selling price, which results in an overhead of $65.34 on the newest version of an air hockey game set. if the air hockey game set costs pyotr tchaikovsky sports $49.32, find the selling price, the markup, and the net profit.

Aflower has 26 chromosomes. to create a new flower,how many would a sperm cell have what is called?