I’m confused and I don’t understand this can someone help?

50%

Explanation:

This is a simple one trait Punnett square.

Because we know that the recessive trait is blue (yy) thanks to the text mentioning SpongeSusie being blue and recessive. Spongebob is yellow with a genotype of Yy or heterozygous. So we need two y to make a blue baby.

Yy X yy = 50% yellow Yy and 50% blue yy

c. because step up transformer steps up the input voltage i.e increases the input voltage  

the number of turns are greater on the secondary side of step up transformer  

transformer does not handle dc current