ANSWER
x = 10
EXPLANATION
We want to find the missing box in the statement given.
Let the box be represented by x:
[tex]x\text{ + (-7) = 3}[/tex]To solve this, move (-7) to the other side, the sign changes:
[tex]\begin{gathered} x\text{ = 3 + (+7)} \\ x\text{ = 3 + 7} \\ x\text{ = 10} \end{gathered}[/tex]The box is 10.
