Question

efetue as operações entre frações 
 3/10 +1/4 = ???

3/4 + 4/5 - 3/10 = ???

Answer 1

$\boxed{\frac{3}{10}+ \frac{1}{4}= \frac{6+5}{20}= \frac{11}{20}}$

$\boxed{ \frac{3}{4} + \frac{4}{5} - \frac{3}{10} = \frac{15+16-6}{20}= \frac{25:5}{20:5}= \frac{5}{4} }$

Answer 2

 3   + 1 =
10     4
mmc (4, 10) = 20
6 + 5 = 11
 20       20

3  +  4   -   3   =
4      5      10
mmc (4, 5, 10) = 20
15 + 16 - 6 =
      20
25 =
20
5
4