Question

the ratio of the masses of flour in two bags is 5 to 7. the heavier bag contains 1120 grams of flour. what is the total mass of flour in both bags?

Answer 1

The ratio between the masses of the flour bags is equal to the ratio oft the numbers 5 and 7.

$7 \div 5 =1.4$
7 is 1.4 times bigger than 5.
That means the heavier bag contains 1.4 times more flour as the other one.
$1120 \div 1.4 = 800$
The smaller bag has a mass of 800 grams.
I guess you can figure out the rest by yourself. ; - )