Question 311274
Hello!
I will show you a few examples
1)  2/3- 2/7 = 2*7/3*7 - 2*3/7*3
=14/21-6/21
=(14-6)/21
=8/21

2)  7/10-9/20= 7*2/10*2 - 9/20
=(14-9)/20
=5/20
=1/4

3)  1/(x+1)-1/(x+2)
=1*(x+2)/(x+1)(x+2)-1*(x+1)/(x+1)(x+2)
=[(x+2)-(x+1)/(x+1)(x+2)
=[x+2-x-1]/(x+1)(x+2)
=1/(x+1)(x+2)