Determine triangulation?

first you take the 25m and convert it to cm to fit the page then in this case 25cm doesn't fit so well so you divide by something, 5 works best in this case so its 5cm. so draw a 5cm line on your page and use a protractor to put the angles on the sides and draw the lines up till they meet on the angles then measure the distance from the point to the line. multiply it by 5 and convert it back in to metres and you have your answer