Answer:
3. x = 3.2; y = -0.6
4. countless experimental equations
7. x = -3.375; y = -12.125
8. x = 42/13; y = 2/13
9. countless experimental equations
10. countless experimental equations
11. 12. (I do not get the questions here because there are values of x and y already)
Explanation:
3. x + 2y = 2 => 6x + 12y = 12 => 6x = 12 - 12y
6x - 3y = 21 => 12 - 12y - 3y = 21 => 15y = 9 => y = 9/15 = 0.6
=> 6x = 12 - 12 x 0.6 = 4.8 => x = 4.8/ 6 = 0.3
4. x - y = 9 => y = x - 9
y = x + 4
=> x - 9 = x + 4 => 9 = 4 (Error) => countless experimental equations
7. y = 1/3. x - 11
=> 3x - 1/3. x + 11 = 2 => 8/3. x = -9/(8/3) = -3.375
=> y = 1/3 x -3.375 -11 = -12.125
8. 3x + 2y = 10 => 9x + 6y = 30 => 6y = 30 - 9x
=> 4x - (30 - 9x) = 12 => 13x = 42 => x = 42/13
=> 6y = 30 - 9 x (42/13) => x = 2/13
9. y = -1/4.x -5
=> 2x + 8 x (-1/4x -5) = 56
=> -40 = 56 => countless experimental equations
10. y = -4x -2
=> 12x + 3 x (-4x-2) = 27
=> -6 = 27 => countless experimental equations