math
posted by Katherine .
kyle had 36 books in hislocker. some were library books, some were textbooks, and the rest were telophone books. the number of library books and textbooks combined equal twice the number of textbooks. the number of textbooks and telephone books combined equals three times the number of library books. how many of each type of book were in kyle's locker??
please help me....i need a chart or a rule to show me how u got it....please

let ..
number of textbooks be x
number of library books by y
number of telephone books by z
x+y+z = 36 (#1)
y+x = 2x  > y = x (#2)
x+z = 3y  z = 3y  x (#3)
back in #1
x+y+z = 36
x + x + (3yx) = 36
x+x+(3xx) = 36
4x=36
x=9
then y=9
z = 18
9 library books
9 textbooks
18 telephone books