Respuesta :

Answer:

9

Step-by-step explanation:

this is because it is 9 and it could be 9

Answer:

First let's find what (5x7) + (5x9) equals;

(5x7) + (5x9)

35 + 45

= 80

Now 80 has to equal to;

5 x (7 + y) ( where 'y' is our unknown number)

So we set up the equation:-

80 = 5 x (7 + y)

80 = 35 + 5y

-35      -35

45 = 5y

/5    /5

9 = y

Let's double check:

80 = 5 x (7 + y)

80 = 5 x (7 + 9)

80 = 35 + 45

80 = 80, we are correct.