Convert both numbers to improper fractions, and to do that, multiply the denominator and whole number, and add the numerator.
If done correctly, you should get 13/7 - 15/11.
Now, we have to find the LCM of both denominators.
77 is the LCM.
77 is the LCM.
You needed to multiply 7 by 11 to get 77, so multiply 13 by 11, too.
13 x 11 = 143
We get 143/77.
Do the same with the other fraction.
You needed to multiply 11 by 7 to get 77. So multiply 15 by 7.
15 x 7 = 105
We get 105/77
Now you can subtract.
143/77 - 105/77 = 38/77