(0,0) represents the cost of 0 bags of candy.
where (1,2) tells us that 1 bag of candy costs $2....(2,4) and 2 bags of candy costs $4.....(3,6) and 3 bags of candy cost $6
0.50 because if you turn 15% into a decimal you get 0.15 and 0.65-0.15 =0.5
Just try it like this. Hope it helps
4x4=16 9x(-6)=-54 16+(-54)=-38 -7x-38=266