<PRE><B>Question 616920</B>
okay, so let us call x + 4y = -7 EQUATION ONE 
               and -4x + 5y = 28 EQUATION TWO

from equation one you can get:

x = -7 -4y (by moving the 4y to the other side (and when doing so changing the sign).

You can then multiply all values by four to give:

4x = -28 - 16y

Now change the signs for all values to get -4x:

-4x = 28 + 16y

you can then substitute this into equation 2:

(28 + 16y) + 5y = 28

16y + 5y = 28 - 28

21y = 0

so y = 0

Then use equation one with a value of y=0:

x = -7

so x= -7 and y=0</PRE>