just subisute values that will work
one easy way is to make one sides equal to only one of the placeholders, like y, and then lug in values in for x exg
x+2y=3
subtract x from both sides
2y=3-x
divideb bith sides by 2
y=-1/2x+3
subsitute valudes for x and get values for y
if x=2 then
y=-1/2(2)+3
y==-1+3
y=2
when x=2, y=2
when y=0 then y=3