Question

a swimmer was 8 feet underwater. then he swam 3 feet deeper.

riku wrote the expression $-8 - 3$.

charlie wrote the expression $-8 + (-3)$.

explain why both riku and charlie are correct.

Explanation:

1. Represent depth with negative numbers: starting depth is $-8$ feet.
2. Swimming deeper means adding more negative depth. Subtracting a positive number ($-8 - 3$) is mathematically equivalent to adding its negative counterpart ($-8 + (-3)$).
3. Both expressions simplify to the same value: $-11$, which correctly represents the final depth. The two expressions use equivalent integer operation rules.

Answer:

Both are correct because subtracting a positive number is mathematically equivalent to adding its negative. $-8 - 3$ and $-8 + (-3)$ are identical operations under integer arithmetic, both resulting in $-11$, which accurately describes the swimmer's final depth of 11 feet underwater.