i just need the work for 11 & 12. i know the answer for 11 is (16,4) and 12 is (5,7) but i don’t know how to work it out to get those answers. (solving a system of linear equations)

i just need the work for 11 amp 12 i know the answer for 11 is 164 and 12 is 57 but i dont know how to work it out to get those answers solving a system of line class=