A rational number (or fraction) is represented as a ratio between two integers, a and b, and has the form \({a \over b}\) where a is the numerator and b is the denominator. An improper fraction (\({5 \over 3} \)) has a numerator with a greater absolute value than the denominator and can be converted into a mixed number (\(1 {2 \over 3} \)) which has a whole number part and a fractional part.

There are 3 4-passenger taxis available so that's 3 x 4 = 12 total seats. There are 17 people needing transportation leaving 17 - 12 = 5 who will have to find other transportation.

The first few multiples of 2 are [2, 4, 6, 8, 10, 12, 14, 16, 18, 20] and the first few multiples of 10 are [10, 20, 30, 40, 50, 60, 70, 80, 90]. The first few multiples they share are [10, 20, 30, 40, 50] making 10 the smallest multiple 2 and 10 have in common.

A factorial is the product of an integer and all the positive integers below it. To solve a fraction featuring factorials, expand the factorials and cancel out like numbers:

\( \frac{6!}{2!} \)
\( \frac{6 \times 5 \times 4 \times 3 \times 2 \times 1}{2 \times 1} \)
\( \frac{6 \times 5 \times 4 \times 3}{1} \)
\( 6 \times 5 \times 4 \times 3 \)
360

By buying two shirts, Ezra will save $11 x \( \frac{45}{100} \) = \( \frac{$11 x 45}{100} \) = \( \frac{$495}{100} \) = $4.95 on the second shirt.

So, his total cost will be
$11.00 + ($11.00 - $4.95)
$11.00 + $6.05
$17.05