a marketing firm determined that , of 200 households surveyed , 80 used neither brand r nor brand b soap , 60 used only brand r soap , and for every household that used both brands of soap , 3 used only brand b soap . how many of the 200 households surveyed used both brands of soap ?
solution for soap r and soap b ( d ) 40
add(add(divide(subtract(200, add(80, 60)), add(3, const_1)), divide(subtract(200, add(80, 60)), add(3, const_1))), const_10)