Let s and g represents the numbers of suits and gowns produced.
The number of zippers used is 2s+g.
The number of buttons used is 5s+8g.
In order to use all of the available zippers and buttons, we must have ...
- 2s + g = 171
- 5s + 8g = 576
Cramer's rule tells you the solution to the system
Is given by
- x = (bf-ey)/(bd-ea)
- y = (cd-fa)/(bd-ea)
Using this rule on the equations for zippers and buttons, we have
... s = (1·576 -8·171)/(1·5 -8·2) = -792/-11 = 72
... g = (171·5 -2·576)/-11 = -297/-11 = 27
72 suits and 27 gowns can be made from available zippers and buttons.
I is C because you use the pythag theorem
5x = 6x-7
subtract 6x from each side
-x=-7
x=7
