Jacob's printing Inc. Has two type of printing presses:model A and Model B. Model A can print 40 books per day and Model B can print 70 books per day. Altogether jacob has 12 printing presses. If he can ptint 600 books in a day then how many of each press does he have?

A=number of a models

b=number of b models

total number of books=abooks+bbooks

abooks=a times number of books per day or 40

bbooks=b times number of books per day or 70

total number of presses is 12 or a+b

so we have 2 equations

40a+70b=600 and

a+b=12

we can use eliminateion

multiply 2nd equation by - 40 and add to top equation

40a+70b=600

-40a-40b=-480 +

0a+30b=120

30b=120

divide both sides by 30

b=4

sub back

a+b=12

a+4=12

minus 4

a=8

he has 8 of the A model machines and 4 of the B model machines