А)3/36 + 7/9, б)2/5 + 3/20

а) 3/36+7/9=3/36+28/36=31/36 б) 2/5+3/20=8/20+3/20=11/20

[latex] \frac{3}{36} + \frac{28}{36} = \frac{31}{36} [/latex] [latex] \frac{8}{20} + \frac{3}{20} = \frac{11}{20} [/latex]