7/8 - 4/5 what is the answer to this thing because i don't know it at all du

7/8-4/5. When subtracting two fractions, we must have a common denominator. A common denominator is a factor in which goes into both 8 and 5.

1.) Common factor: 45. 45 goes into and 8 and 5. If we list out all the factors of 8 and 5, 45 will be the lowest common factor.

2.) We need to multiply by a number to get 45 for each denominator. We can a one-step equation to figure out what we need to multiply 8 by and 5 by to get 45.
X=the factor of 8 that will get us 45.
8x=45
8x/8=45/8
x=5.625.
Y=factor of 5 that will get us 45.
5y=45
5y/5=45/5
y=9.

3.) We now know that we need to multiply 8 by 5.625 and 5 by 9 in order to get 45 as the denominator for both fractions.
7/8x5.625-4/5x9
7/45-4/45.

4.) Whatever is done to the denominator must be done to the numerator.
7x5.625/45-4x9/45
39.375/45-36/45

5.) We now have common denominators, so we simple subtract the numerators ONLY. We DO NOT subtract the denominators.
39.375/45-36/45=3.375/45.

Therefore, 3.375/45 is your answer.