Final answer:
The equivalent expressions are
,
, and

Step-by-step explanation:
The expression
can be simplified using the rule of multiplying exponentiated quantities: when multiplying the same base with different exponents, we can add the exponents together. In this case, we have 5 raised to the power of 3 multiplied by 5 raised to the power of x. Therefore, the equivalent expressions are:
These expressions have combined the exponents by addition or multiplication, resulting in equivalent forms of the original expression.