Ben M. answered • 02/11/16

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Let d = # desktops

l = # laptops

Then d + l = 15

Also we know that 11700 = 700l + 1000d

from the first equation, d = 15 - l

substitute this into the second equation:

11700 = 700l + 1000*(15 - l)

-3300 = -300l

l = 11

and therefore d = 4

Checking the total cost

11*700 + 4*1000 = 7700 + 4000 = 11700