First, try rewriting all of the subtraction as addition, then attempt to solve by simplifying like terms.

$\begin{align*} 3p + \left(−7\right) + 9 + \left(−2p\right) &= p + 2 \\ p + 2 &= p + 2 \\ p &= p \end{align*}$

Since $p = p$ (or $2 = 2$, depending on how you solved the problem),
$p$ can equal any number.

One strategy is to rewrite all of the subtraction within the problem as addition.
$−y² + 2 = y² + −5 + −2y²$

Now simplify, starting with combining like terms and then with isolating the variable.

$\begin{align*} −y² + 2 &= −y² + −5 \\ 2 &= -5 \end{align*}$

No solution because $2$ is not equal to $−5$.