Question 241700
[what is 4x + 3y = 31]
If this is a linear equation then:
3y=-4x+31
y=-4x/3+31/3
{{{ graph( 300, 200, -6, 15, -10, 12, -4x/3 +31/3) }}} (graph 300x200 pixels, x from -6 to 15, y from -10 to 12, -4x/3 +31/3). 
There are multiple solutions :
(4,5)
5=-4*4/3+31/3
5=-16/3+31/3
5=15/3
5=5
(1,9)
9=-4*1/3+31/3
9=-4/3+31/3
9=27/3
9=9