Question

What fraction part remains uncovered if 3 rectangles are covered

Answer 1

At the beginning, you begin with one whole that's been split into 25 pieces, or 25ths. Before you cover any of them up, you still have all 25, so you have 25 25ths, or, as a fraction, $\frac{25}{25}$. Next, you take away 3 of those 25ths, or $\frac{3}{25}$, which leaves you with $\frac{25-3}{25}$, or $\frac{22}{25}$.