I believe trigo ratios are usually not covered in S1.
Draw a line to join BD.
Use area of triangle ABD to solve:
Area of triangle ABD = 1/2 * 11 * 8 cm² = 1/2 * 10 * BX cm²
BX = 8 *11/10 cm = 8.8 cm
Typo. Suppose to be BX = Sin(53.1) X 11 = 8.8cm###