Question

I need help I need to understand

Answer 1

You can use the method of pythagorean theorem.
                         a² + b² = c²
or in your case, 14² + 15² = x²
14² = 14 * 14 = 196
15² = 15 * 15 = 225
    196 + 225 =  451
        √451 = 21.237
             or 21.23676058159
*I rounded to the nearest thousands place