## Explanation

### Simplifying the Fraction

To simplify the fraction $\frac{28}{40}$ to its simplest form, we need to find the **greatest common divisor (GCD)** of the numerator and the denominator.

### Finding the GCD

The GCD is the largest number that divides both the numerator (28) and the denominator (40) without leaving a remainder. We first list the factors of each number:

**Factors of 28**: $1, 2, 4, 7, 14, 28$**Factors of 40**: $1, 2, 4, 5, 8, 10, 20, 40$

The common factors are **1, 2, and 4**. Among these, the largest factor is **4**.

### Simplifying the Fraction

We divide both the numerator and the denominator by their GCD:

$\frac{28 \div 4}{40 \div 4} = \frac{7}{10}$Thus, the fraction $\frac{28}{40}$ in its **simplest form** is: