Atextbook store sold a combined total of 480 history and math textbooks in a week. the number of history textbooks sold was two times the number of math textbooks sold. how many textbooks of each type were sold?

let h = history books, and m = math books

h + m = 480

h = 2m

plug in 2m for h

2m + m = 480

3m = 480

m = 480/3

m = 160

Plug in 160 for m in one of the equations

h + m = 480

h + 160 = 480

h = 480 - 160

h = 320

h = 320, m = 160

hope this helps