Q1. Add 12 to both sides 3v=27. Divide by three on both sides v=9
Q2. subtract 12 to both sides 4n= -8. divide by 4 on both sides n=-2
Q3. subtract 8 to both sides 5x=-10. divide by 5 on both sides x=-2
Q4. subtract 9 to both sides w/4=-14. multiply by 4 on both sides w=-56
Q5. add 5 to both sides 10=1/2x. divide by 1/2 to both sides x=5
Q6. subtract 9 to both sides a/6=-1. multiply by 6 on both sides a=-6
Q7. add 11 to both sides 6a=24. divide by 6 on both sides a=4
Q8. add 9 to both sides d/4=6. multiply by 4 on both sides d=24
Q9. add 7 to both sides -2t=10. divide by -2 on both sides t=-5
The whole thing is to isolate the variable