Building and solving an equation to model the situation, it is found that he collected 78 pieces of candy on Hallowen night.
Solving for x, we find how many pieces of candy he collected, thus:
[tex]x - 7 - 0.1x = 63[/tex]
[tex]0.9x = 70[/tex]
[tex]x = \frac{70}{0.9}[/tex]
[tex]x = 77.8[/tex]
Rounding, he collected 78 pieces.
A similar problem is given at https://brainly.com/question/24812278