x+4y=8 2x-5y=29

x+4y=8  2x-5y=29

Using the first equation, subtract 4y from both sides

So x  = 8 - 4y       and subbing this into the second equation foe x, we have

2(8 - 4y) - 5y = 29

16- 8y - 5y = 29   simplify

16 - 13y = 29       subtract 16 from both sides

-13y = 13             divide both sides by -13

y = -1 

And x = 8 - 4(-1)  = 8 + 4  = 12