Hola por favor ayudame

In a class, there are 12 girls. if the ratio of boys to girls is 5: 4 how many boys are there in the class

Can someone me on this math worksheet about finding the given variable for these angles, and whether the triangles are similar. i really need these answers i’m so confused: ( !

Consider u = {x|x is a negative real number}which is an empty set? o {x|x eu and x has a negative cube root}o {x|x eu and x has a negative square root}{x|x eu and x is equal to the product of a positive number and -1}{x|x eu and x is equal to the sum of one negative and one positive number?