Find all natural numbers which are equal to their digit sum multiplied by 3

Which of the following correctly justifies statement four of the two column proof? a. corresponding angles theorem b. transitive property of equality c. vertical angle theorem d. substitution property of equality

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.

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