your equation is the following:
11 7/7 - (-8 3/7)
the first step to solving this is to know that when there is a
"-" sign in front of the parenthesis, you need to change the sign of each term in the parenthesis.
11 7/7 + 8 3/7
now, add the whole numbers and the fractional parts of the mixed numbers separately.
(11 + 8) + (

)
add the whole numbers together
19 + (

)
now add the fractions together
19 + 10/7
next, convert the improper fraction to a mixed number
19 + 1 3/7
now, you will write the mixed number as a sum of the whole number and its fractional part.
19 + 1 + 3/7
add the numbers together
20 + 3/7
finally, write the sum of the whole number and the fraction as a mixed number
20

let me know if you have any further questions
:)