a)
1,2x + 2/3x = 1 2/10x + 2/3x = 1 6/30x + 20/30x = 1 26/30x = 1 13/15x
b)
[tex] \frac{1}{4} x + \frac{5}{6} x - \frac{1}{2} x = \frac{3}{12} x + \frac{10}{12} x - \frac{6}{12} x = \frac{13}{12} x - \frac{6}{12} x = \frac{7}{12} x[/tex]
