1) Start by finding a common denominator for x:12 and x:8, which is 24. Rewrite the equation as 2x:24 - 3x:24 = 4:24. Combine like terms to get -1x:24 = 4:24, x = -4.

2) Start by finding a common denominator for 13x:21 and 9x:14, which is 42. Rewrite the equation as 26x:42 + 27x:42 = -42. Combine like terms to get 53x:42 = -42, x = -42/53.

3) Start by finding a common denominator for -3x:10 and x:6, which is 30. Rewrite the equation as -9x:30 - 5x:30 = 5:30. Combine like terms to get -14x:30 = 5:30, x = -5.