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.