Question 207839
Did you copy this one correctly?  Should the second equation should be 5=x+y?  Either one is somewhat ugly, so I'll go with your problem as stated.


In the second equation, subtract y from each side.
5y=x+y
4y=x


Substitute this into the first equation for x:
4x+y=5
4(4y)+ y = 5
16y + y=5
17y=5
y=5/17


To solve for x, go back to the equation x=4y
x=4y
x=4(5/17)
x=20/17


The solution is (20/17,5/17)


Check in the OTHER equation
4x+y =5
{{{4(20/17)+(5/17) = 5}}}
{{{80/17 +5/17=5}}}
{{{85/17=5}}} 

It checks!!


R^2