x+y=43
4x=2y+4
In first equation subtract 'y' from both sides:
x=43-y
In second equation substitute 'x' from first equation:
4(43-y)=2y+4
Simplify by dividing by 2,
2(43-y)=y+2
Open parantheses,
86-2y=y+2
Add '2y' to both sides,
86=3y+2
Subtract 2 from both sides,
84=3y
Divide by 3,
y=28
Then,
x=43-y=43-28=15