Idont understand these questions. a) ali is 26 years old. if his sister laura is x years younger than ali, write an expression for the sister's age in terms of x. b) write and expression for the area of a triangle whose base is 8cm and its height is x cm more than the base. c) write an expression for the number of adults in a theatre that has 760 people in attendance of which x are children. d) write an expression for the cost of x packets of tea if ine packet costs $2.79.