From here, take one of two avenues:
First Method: Calculus
The area of the triangle is the area under the curve (LS line, in this case) bounded from below by the Y-axis ( ) and from above by the X-axis ( ). The lower X-limit is 0 and the upper X-limit is the solution to , which is .
Second Method: Find the triangle's coordinates, compute the area of the relevant rectangle, then take half that number. That is, .