while x is -a million the respond is 15 while x is 0 that's 8 while x is a million that's 3 while x is two that's 0 while x is 3 that's -a million while x is 4 that's 0 while x is 5 that's 3 while x is 6 that's 8 and for the 2nd question, interior the 1st equation x=6-y and substitute this interior the 1st equation which will provide you 6-y=12+y so 2y=-6 and y= -3 . understanding y= -3 from first equation you will discover x surely as x + (-3)=6 so x=9