STUCK ON PART (III) hellp

(i) find the inverse of 4 1 k , k doesnt =5

3 2 5

8 5 13

DONE

(ii) solve the smultaneous equation

4x + y + 7z = 12

3x + 2y + 5z = m

8x + 5y +13z = 0

giving x,y,z in terms of m,,,DONE i got x= -6-11m

y= -6+2m

z=6+6m correct i think

(iii) find the value of p for which the simultaneous equations have solutions, and fn general solution in this case

4x+y+5z=12

3x+2y+5z=p

8x+5y+13z=0

how does it have solutions??,ithought this was just det doesnt = 0,,confused as to how im supposed to do this part when k doesnt = 5 either,,,,,,help pls