1/

$\frac{5}{7} + \frac{3}{18}$

$\frac{5}{7} + \frac{1}{6}$

= $\frac{ 5 x 6}{7x6} + \frac{1x7}{6x7} $

= $\frac{30}{42} + \frac{7}{42}$

=$ \frac{37}{42}$

2/

$\frac{15}{24} + \frac{12}{16}$

= $\frac{5}{8} + \frac{3}{4}$

= $\frac{5}{8} + \frac{6}{8}$

= $\frac{11}{8}$

Chữ "x" là dấu nhân nha em

@Team IQ vô cực

Đáp án:

 

Giải thích các bước giải:

$a,\dfrac{5}{7}+\dfrac{3}{18}$

$=\dfrac{5×18}{7×18}+\dfrac{3×7}{18×7}$

$=\dfrac{90}{126}+\dfrac{21}{126}$

$=\dfrac{90+21}{126}$

$=\dfrac{111}{126}$

$=\dfrac{111:3}{126:3}$

$=\dfrac{37}{42}$

$b,\dfrac{15}{24}+\dfrac{12}{16}$

$=\dfrac{15:3}{24:3}+\dfrac{12:4}{16:4}$

$=\dfrac{5}{8}+\dfrac{3}{4}$

$=\dfrac{5×4}{8×4}+\dfrac{3×8}{4×8}$

$=\dfrac{20}{32}+\dfrac{24}{32}$

$=\dfrac{20+24}{32}$

$=\dfrac{44}{32}$

$=\dfrac{44:4}{32:4}$

$=\dfrac{11}{8}$

chúc bạn học tốt!