A) Jamar rewrote the first equation as -2x + 10y = -4. He had justification for doing this because he multiplied all parts of the expressions on both sides of the equation by the same factor, -2.
B) Jamar combined -2x + 10y = -4 with the other equation, 3x-10y=11, to get x=7. To do this, Jamar used combination, combining each of the different parts of the equations together. The y variables cancel out, and the x variables leave 1x, and we subtract 4 on the right side of the equation, leaving x = 7.
C)The solution of the system in an ordered pair (x,y) is (7, -1). You can get the y variable by substituting the x variable that we know equals 7, back into either of the beginning equations, to get the y value.
D) You know, without graphing, that the graph of 4x-15y=13 passes through the point whose coordinates are the solution of the system, because if we plug in the ordered pair (7,-1) into the equation it is a true statement, meaning that the variables are a solution this equation too. Therefore, if it were to be graphed, it would go through the point (7, -1).
