Question 174589
c. 4x + y =17 or y=-4x+17 (red line)
2x + 3y=21 or 3y=-2x+21 or y=-2x/3+21/3 or y=-2x/3+7 (green line).
{{{ graph( 300, 200, -6, 5, -10, 10, -4x +17, -2x/3 +7) }}} (graph 300x200 pixels, x from -6 to 5, y from -10 to 10, of TWO functions -4x +17 and -2x/3 +7). 
ANSWER (3,5)
d. 18x + y=42 or y=-18x+42 (red line)
6x-3y=-6 or -3y=-6x-6 or y=-6x/-3-6/-3 or y=2x+2 (green line).
{{{ graph( 300, 200, -6, 5, -10, 50, -18x +42, 2x +2) }}} (graph 300x200 pixels, x from -6 to 5, y from -10 to 50, of TWO functions -18x +42 and 2x +2).
ANSWER (2,6)