Answer:
This is actually false according to most accepted definitions - a rectangle that has equal sides would be a square, and thus also a rhombus.
Explanation:
The definition of a rhombus is that it has 4 equal sides.
Also, the definition of a rectangle is that it has two pairs or equal sides, and all angles are 90 degrees.
So a square is a special case of a rectangle. And a square is also a special case of a rhombus.
Meaning that a square is both a rhombus and a rectangle, so any rectangle with equal sides would also be a rhombus.