Question

How to you solve 7 7/10- 3 4/5

Answer 1

Make them both improper fractions.
77/10 - 19/5

Give them common denominators (multiply the second fraction by 2)
77/10 - 38/10

Subtract 
39/10 = 3 9/10

Answer 2

Question :
How to you solve 7 7/10- 3 4/5
Answer :
Convert to improper fractions. 
$\frac{77}{10} - \frac{19}{5}$

Equate the denominator :
$\frac{77}{10}- \frac{19}{5} = \frac{77}{10} - \frac{38}{10}$

subtract both fractions :
$=\frac{39}{10}$

or equal :
$3 \frac{9}{10}$