26 is what percent of 325

Two customers went to a post office. first customer paid $12 for 14 and 5 envelopes the second paid 24.80 for 10 postcards and 15 envelopes. what is cost of each envelope?

What is the area of the wall surface of a room that is 16’ x 18’ with 9 ceilings?

The equation for two lines in the coordinate plane are 2dx+y=4 and -6x+y=3, where d represents an unknown value. what value(s) of d would make these lines parallel?