12. 7(p + 3) + 9 = 5(p - 2) - 3p

Explanation:

Step1: Expand both sides

$7(p + 3)+9=7p+21 + 9=7p + 30$, $5(p - 2)-3p=5p-10-3p = 2p-10$. So the equation becomes $7p + 30=2p-10$.

Step2: Move like - terms to one side

Subtract $2p$ from both sides: $7p-2p + 30=2p-2p-10$, which simplifies to $5p+30=-10$.

Step3: Isolate the variable term

Subtract 30 from both sides: $5p+30 - 30=-10 - 30$, getting $5p=-40$.

Step4: Solve for $p$

Divide both sides by 5: $\frac{5p}{5}=\frac{-40}{5}$, so $p=-8$.

Answer:

$p=-8$