The equation to find the curved surface area of a cone is A=πHr, where r denotes the radius of the base of the cone, and H denotes the slant height of the cone. In this case, we know A (594), r (7) and π (a constant = 3.1415...). Our only unknown is H. We therefore rearrange the equation to make H the subject. This will give H=A÷(πr). Plug in the numbers to get H=594÷(π×7) and you end up with H=27. (You actually get 27.01..., as π goes on for an infinite number of decimal places, so make sure you round your answer to the precision stated in the question)