Step 1) Solve the first equation for x:
3x - 2y = 9
3x - 2y + color(red)(2y) = 9 + color(red)(2y)
3x - 0 = 9 + 2y
3x = 9 + 2y
(3x)/color(red)(3) = (9 + 2y)/color(red)(3)
(color(red)(cancel(color(black)(3)))x)/cancel(color(red)(3)) = 9/3 + (2y)/3
x = 3 + 2/3y
Step 2) Substitute 3 + 2/3y for x in the second equation and solve for y:
2x + 3y = 12 becomes:
2(3 + 2/3y) + 3y = 12
(2 * 3) + (2 * 2/3y) + 3y = 12
6 + 4/3y + 3y = 12
6 + 4/3y + (3/3 * 3y) = 12
6 + 4/3y + 9/3y = 12
6 + 13/3y = 12
-color(red)(6) + 6 + 13/3y = -color(red)(6) + 12
0 + 13/3y = 6
13/3y = 6
color(red)(3)/color(blue)(13) xx 13/3y = color(red)(3)/color(blue)(13) xx 6
cancel(color(red)(3))/cancel(color(blue)(13)) xx color(blue)(cancel(color(black)(13)))/color(red)(cancel(color(black)(3)))y = 18/13
y = 18/13
Step 3) Substitute 18/13 for y in the solution to the first equation at the end of Step 1 and calculate x:
x = 3 + 2/3y becomes:
x = 3 + (2/3 xx 18/13)
x = 3 + (2/color(red)(cancel(color(black)(3))) xx (color(red)(cancel(color(black)(18)))6)/13)
x = 3 + 12/13
x = (13/13 xx 3) + 12/13
x = 39/13 + 12/13
x = 51/13
The solution is: x = 51/13 and y = 18/13 or (51/13, 18/131)