Ican't figure out how to find the area of question d. i know i need the height and i know what to do after that but i have no clue how to find the height.

Imagine there is a right angle triangle formed with the 30 degree angle and the 10 cm side forming the hypotenuse. Now, you can use trigonometry to calculate the height of this triangle, which is the same as the height of this shape.
So sin(30) =  height/10
So, height = 5 cm

Chemistry is a stone g subject hope you find the answer