SOLUTION:
Factorising to find factors of the trinomial -
15x^2 + 13x - 20 = 0
15x^2 + 25x - 12x - 20 = 0
5x ( 3x + 5 ) - 4 ( 3x + 5 ) = 0
( 3x + 5 ) ( 5x - 4 ) = 0
Solving for x -
3x + 5 = 0
3x = - 5
x = - 5 / 3
OR
5x - 4 = 0
5x = 4
x = 4 / 5
Hope this helps! :)
Have a lovely day! <3