辛玲起初有 360 颗蓝色、绿色和白色的珠子。在用去 $\tfrac{1}{4}$ 的蓝色珠子、$\tfrac{2}{3}$ 的绿色珠子和 $\tfrac{8}{9}$ 的白色珠子后，她剩下的每种颜色的珠子数量相等。求剩下的蓝色珠子数量。

1. Find the fraction of beads left for each colour.

Fraction of blue beads left = $1 - \frac{1}{4} = \frac{3}{4}$
Fraction of green beads left = $1 - \frac{2}{3} = \frac{1}{3}$
Fraction of white beads left = $1 - \frac{8}{9} = \frac{1}{9}$

2. Make the numerators of the fractions equal to represent the equal number of beads left.

Since the number of beads left for each colour is equal, we make the numerators the same (LCM of 3, 1, and 1 is 3):
$\frac{3}{4}$ of blue beads = $\frac{3}{9}$ of green beads = $\frac{3}{27}$ of white beads

This means the number of beads left for each colour is $3$ units.

3. Find the total number of units at first and the value of 1 unit.

Total units at first = $4 + 9 + 27 = 40$ units
$40$ units = $360$
$1$ unit = $360 \div 40 = 9$

4. Calculate the number of blue beads left.

Number of blue beads left = $3$ units
$3 \times 9 = 27$