9/10 + -4/5 help please

Answer:
1/10
Step-by-step explanation:
First you've got to find common denominators. The common denominator would be 10 since 10 is divisible by 5 and 10. That means you've got the change the denominator of -4/5. Multiply both the numerator and denominator by 2 to grt -8/10.
Then all you have to do is:
9 + -8 1
——— = —
10 10
Khan academy also has some great videos on this if you're confused.