At Shayna's Printing Company LLC there are two kinds of printing presses: Model A which canprint 40 books per day and Model B which can print 70 books per day. The company owns 13total printing presses and this allows them to print 820 books per day. How many of each type ofpress do they have?

There are "3" Model A printing press & "10" Model B printing press

Step-by-step explanation:

Let there be "a" model A printing press

Let there be "b" model B printing press

There are 13 total, so we can write:

a + b = 13

or,

a = 13 - b

Also, a's rate is 40 books per day and b's rate is 70 books per day and total they print 820 books per day, so we can write:

40a + 70b = 820

Now, we substitute 1st equation (2nd form) into this equation and thus solve for b first:

Sincer we know a = 13 - b, we can say:

a = 13 - 10

a = 3

There are "3" Model A printing press & "10" Model B printing press

c is the final : )