Solution
for this case we know this:
3x -29 + 8y +17 = 180
And solving we have:
3x + 8y = 192
8y -17 = 6x -7
8y -6x = -24
Multiplying the first equation by 2 and adding to the second one we got::
6x + 16y = 384
-6x +8y = -24
______________
24y = 360
y= 15
And x= (192- 8*15)/ 3 = 24