First you want to write 7x as a sum or difference: 15x-8x Now, the expression would look like this: 10x^2+15x-8x-12 Next, factor out the 5x and -4 from the expression: 5x(2x+3)-4(2x+3) Now, factor out the 2x+3 from the expression and you have your answer: (2x+3)(5x-4)