If you want to avoid doing the maths I think you can draw the problem out (assuming the world is a flat piece of paper and the source is located on the same piece of paper with you)
From the timings given you can work out the distance from location B and C to the wavefront when it hits point A (4 x 330 and 6 x 330).
If you then draw a circle centered at point B with radius 1320m, and a circle centered C with radius 1980m, then there is only one circle you can draw that intersects point A, and is tangent with the circles drawn at B and C. The center of that circle is the source (with an appropriate radius of error for timing measurement and distance measurement between A, B, and C)
From the timings given you can work out the distance from location B and C to the wavefront when it hits point A (4 x 330 and 6 x 330). If you then draw a circle centered at point B with radius 1320m, and a circle centered C with radius 1980m, then there is only one circle you can draw that intersects point A, and is tangent with the circles drawn at B and C. The center of that circle is the source (with an appropriate radius of error for timing measurement and distance measurement between A, B, and C)
https://imgur.com/a/tqV0ToU