Answer :
a (70 books/day) A=number of model A
b (55 books/day) B =number of B , A=number of a then
A+B =14 ........ A=14-B
aA+bB =905
70(14-B) +55B =905
980-70B+55B=905
-15B=-75
B=-75/-15 =5
A=14-B=14-5=9
b (55 books/day) B =number of B , A=number of a then
A+B =14 ........ A=14-B
aA+bB =905
70(14-B) +55B =905
980-70B+55B=905
-15B=-75
B=-75/-15 =5
A=14-B=14-5=9