[tex]a)x + \frac{1}{3} - 2.5 = \frac{x}{2} \\ \\ x + \frac{1}{3} - \frac{5}{2} = \frac{x}{2} \\ \\ x - \frac{13}{6} = \frac{x}{2} \\ \\ 6x - 13 = 3x \\ \\ 6x - 3x = 13 \\ \\ 3x = 13 \\ \\ x = \frac{13}{3} [/tex]
b)13-2x=7,5-x
13-2x+x=7,5
-2x+x=7,5-13
-x=7,5-13=-5,5
=>x=5,5