To make the estimate of the substraction of the mixed numbers we use the fraction that is accompaning the whole number. If the number is less than 1/2 we say that the number is closer to the whole number before the fraction, if it is 1/2 or more then we add one to the whole number.
For the first number
This is approximate to 5 because 1/4 is less than 1/2
For the second number
This is approximate to 4 because 8/9 is greater than 1/2.
ESTIMATE
To pass a mixed number into a fraction we use the following procedure
Pass both mixed numbers
To find the exact value
answer
The exact value of the substraction is