Hi I did my working on paper. You can see it in the photo.
Total discount will be 35%.
Manipulate the first equation to
y = 22-7z
Then substitute in the second to find z
8(22-7z) + 7z = 127
176-56z+7z = 127
-49z = -49
z = 1
So y = 22-7(1) = 22-7 = 15
y = 15; z = 1
66
Difference means subtract. So, 101-35=66