Final answer:
The expression 45 is equivalent to 25 and the expression 21 is equivalent to 2 × 5.
Step-by-step explanation:
The expression 45 is equivalent to 25. By adding the two top arrows or subtracting the two bottom ones, we get the same number, matching the dashed arrow on the right.
The expression 21 is equivalent to 2 × 5. When picking both exponents as 2, there is ambiguity. But if we interpret it as multiplication, we get 2 × 2 = 4, and then adding 1 gives us 5.
None of the given explanations match the remaining expressions, so it is not possible to determine their equivalence.