I'm trying to teach math to my 7 year old daughter. I'm teaching following type of equations. $\cdots - x = y$
I'm able to explain her the rule that:
when $\cdots- x = y$, we can always take $x$ (value on the left of equation) to the other side of $=$ sign and flip( $-$ to $+$ and vice versa), $-$ to $+$ and get the answer.
Meaning when $\cdots - x = y$, we can always do $\cdots = y + x$ and get the answer.
This rule works for \begin{align*} x + \cdots &= y \\ \cdots + x &= y\\ \cdots - x &= y \\ \end{align*}
But it doesn't work for $x - \cdots = y$. Because if you apply the rule, you get - (answer) and not just ( answer )
My question is given that I'm trying to teach this to 7 year old, is there any better method where one rule would cover all 4 cases? Any ideas, thoughts...
\begin{align*} - x + \cdots &= y\\ -\cdots + x &= y\\
- \cdots - x &= y\\
- x - \cdots &= y \end{align*}