Question

Guys help me please with this.

Answer 1

$\frac{3}{10} + ( - \frac{4}{7} ) =$

$\frac{3}{10} - \frac{4}{7} =$

3 x 7 = 21

10 x 4 = 40

10 x 7 = 70

$= \frac{21 - 40}{70}$

$= \frac{ - 19}{70}$

$= - \frac{19}{70}$

So, the number that belongs in the green box is 19.

Answer 2

Answer:

$\large\boxed{-\dfrac{19}{70}\to\boxed{19}}$

Step-by-step explanation:

$\dfrac{3}{10}+-\dfrac{4}{7}=\dfrac{3}{10}-\dfrac{4}{7}\\\\\text{find the common denominator}\ LCD(10,\ 7)=70\\\\\dfrac{3}{10}=\dfrac{3\cdot7}{10\cdot7}=\dfrac{21}{70}\\\\\dfrac{4}{7}=\dfrac{4\cdot10}{7\cdot10}=\dfrac{40}{70}\\\\=\dfrac{21}{70}-\dfrac{40}{70}=\dfrac{21-40}{70}=-\dfrac{19}{70}$