Step 1. Find the LCD (Least Common Denominator)
LCD = 12
Step 2. Make the denominators the same as the LCD
3 * 3/4 * 3 - 11/12
Step 3. Simplify Denominators are now the same
9/12 - 11/12
Step 4. Join the denominators
9 - 11/12
Step 5. Simplify
- 2/12
Step 6. Simplify 2/12 to 1/6
Answer is for 2. is: -1/6
Now let's do number 4.
Step 1. Convert 1 9/10 to an improper fraction
1 * 10 + 9/10 - 2/5
Step 2. Simplify 1 * 10 to 10
10 + 9/10 - 2/5
Step 3. Simplify 10 + 9 to 19
19/10 - 2/5
Step 4. Find the LCD (Least Common Denominator) of 19/10, 2/5
LCD = 10
Step 5. Make the denominators the same as the LCD
19/10 - 2 * 2/5 * 2
Step 6. Simplify. Denominators are now the same
19/10 - 4/10
Step 7. Join the denominators
19 - 4/10
Step 8. Simplify
15/10
Step 9. Simplify
3/2
Step 10. Convert to a mixed fraction
Answer for 4. is: 1 1/2