Firstly: multiply the two first parenthesis:
(5x+6)(x-1)=5x^2-5x+6x-6=5x^2+x-6
then: subtract the last parenthesis from what we have gotten:
5x^2+x-6 - (2x^2-5x+3) = 5x^2+x-6 - 2x^2+5x-3 = 3x^2+6x-9
then equate it to zero:
3x^2+6x-9=0
take 3 as a common factor:
3(x^2+2x-3)=0
x^2+2x-3=0
then solve this quadratic for x:
by factoring: (x+3)(x-1)=0
x=-3
x=1
Done!