Step 1: Simplify the left side of the equation 3a•(-9)=12-(-9) by multiplying 3a by -9.
-27a = 12 + 9

Step 2: Simplify further to combine like terms.
-27a = 21

Step 3: Divide both sides by -27 to solve for a.
a = -21/27
a = -7/9

Therefore, the solution to the first equation is a = -7/9.

Step 1: Simplify the left side of the equation (5a+2)•2=8-2a by multiplying the terms inside the parenthesis.
10a + 4 = 8 - 2a

Step 2: Move all terms containing 'a' to one side of the equation by adding 2a to both sides.
10a + 2a + 4 = 8

Step 3: Combine like terms on the left side of the equation.
12a + 4 = 8

Step 4: Subtract 4 from both sides of the equation to get all terms with 'a' on one side.
12a = 4

Step 5: Divide by 12 on both sides to solve for 'a'.
a = 4/12
a = 1/3

Therefore, the solution to the second equation is a = 1/3.