Calculus Help The upper right-hand corner of a piece of paper, 30 centimeters by 20 centimeters fold

The upper right-hand corner of a piece of paper, 30 cm by 20 cm, as in the figure, is folded over to the bottom edge. How would you fold it so as to minimize the length of the fold? In other words, how would you choose x to minimize y?

#Calculus
#Derivative