Sum of rational expression 9/xy + x^2/y

Jonathan can type 20 documents in 40 minutes ,and susan can type it in 30 minutes and jack can type it in 24 minutes working together ,how much time will it is take them type the same document

Annabelle's homework is 75% it took her three hours how long should she estimate it will take her to complete her homework.

Brent paid for 6 avocados with a $20.00 bill. he received $10.40 in change. construct and solve an equation can be used to find the price , of each avocados