1x+3y = 12 Solve for both, show work

Answer 1

x=12-3y
> sub back to 1x+3y=12
1(12-3y)=12
y = 12-3y=12
y = -3y=0
y = 0
>sub y=0 back into 1x+3y=12
1x+0+12
x = 12

answer = x=12, y=0

Answer 2

a single equation with two unknowns has no unique solution
... the values of the variables are interrelated

the solution is a line

in slope-intercept form ... y = -1/3 x + 4