-1,6 and -7,8 are correct answers though, if you switch x and y by those numbers respectively you do end up with a correct statement

3*(-1,6)-(-7,8 )=3
7,8-4,8=3

(4*(-1,6))-(3*(-7,8 ))=17
23,4-6,4=17

i believe there are multiple answers to this specific one