X+x+20+2x=180
4x+20=180
4x=160
x=40
X = {3.898979486, -5.898979486}
x = {3.9 x -5.9}
The entry in row 1, column 1 of
is

(i.e. the dot product of row 1 of
and column 1 of
)
The entry in row 1, column 2 of
is

The second option is the correct answer.
Rule: lines that are parallel have equal gradients.
Therefore y=-4/3x + b.
To find b, you must sub the point (6,2) into the equation y=-4/3x + b.
2= -4/3 x 6 + b
b=-10 (using algebra to solve)
Therefore y=-4/3x - 10.