Question

The missing term $(?)$ in $-9-?=-2$ is .

Answer 1

Need to find the missing term $(?)$ in $-9-?=-2$.

We are going to find out $(?)$ using subtraction by chip model.

Given equality: $-9-?=-2$

Let's consider a red chip represents $‘‘-1"$.

$\underset{–}{\text{Step 1:}}$ Subtract $-2$ from both L.H.S and R.H.S
$-9-?=-2\Rightarrow -9-?-\underset{–}{(-2)}=-2-\underset{–}{(-2)}\Rightarrow -9-?-\underset{–}{(-2)}=0$
($\because$ Taking out $2$ red chips from $2$$)$



$\underset{–}{\text{Step 2:}}$ Find the value of $-9-\underset{–}{(-2)}$, which represents taking out $2$ red chips from $9$ red chips, and it lefts us with $7$ red chips (equivalent to $-7$)


$\underset{–}{\text{Step 3:}}$ Substituting $-9-\underset{–}{(-2)}=-7$, we get $-7-?=0$, from which it is clear that if we remove all $7$ red chips, we left with $0$ red chips


$\therefore$ The missing term $(?)$ in $-9-?=-2$ is $-7$.