Let the numbers be 7x and 4x
According to question
7x-4x =57
3x =57
X=57/3
X=19
So the numbers are
7x=7*19=133
4x=4*19=76
Lets just say hypothetically that x=7. So to find the odd number before 7 we need to subtract a number. The odd before 7 is 5 which is 7-2. So by subtracting 2 from a odd value you get the odd value befire it so your equation is x-2
20% = 1/5 of 100%
3 is 1/5 of ____
3 * 5 = 15
3 is 1/5 of 15
3 is 20% of 15