Can someone please help me with these 3 problems? Tysm!! Will give brainleist!!

Answer:
8) 14
10) 1
12) 81
Step-by-step explanation:
For number eight, you have to multiply out by 2. For example,
9 x 2= 18
2 x 2= 4
7 x 2= 14
For number ten, you have to subtract by 9. For example,
51 - 42= 9
10 - ___= 9
the space would be 1 because 10-1 equals 9
For number 12, you have to multiply out by 9
5 x 9=45
10 x 9= 90
9 x9= 81