Answer: (gcf)=3
Step-by-step explanation: 15x+18y+3z+21=0/-21
3(5x +6y+ z) = 0 -21
3(5x +6y+z)= -21(/3)
5x+6y+z= -7
30x+ 30y +z =-7/x30
30(x+y)+z= -210(/30)
x+y+z= 70
so now
x=0
y=0
z=70
..................
x=1
y=1
z=68
...............
x=2
y=2
z=66
................
x=3
y=3
z=63
.....................
x=4
y=4
z=62
......................
x=5
y=5
z=60
...................
etc u can also consider the negative values so as a conclusion 3 is the greatest common factor :)
