Answer :
you can solve this by saying $1000 is equal to 250 + $2 * the amount of posters (x)
1000=250+2x
1000-250=2x
750=2x
x= (750/2)
x =375 posters
1000=250+2x
1000-250=2x
750=2x
x= (750/2)
x =375 posters