(5x - 4)(2x - 1) - (x - 7)(3x + 5)
FOIL on the first part
10x^2 - 5x - 8x + 4 - (x - 7)(3x + 5)
10x^2 - 13x + 4 - (x - 7)(3x + 5)
FOIL on the second part
10x^2 - 13x + 4 - (3x^2 + 5x - 21x - 35)
Now the - hits each piece of the second part like this
10x^2 - 13x + 4 - 3x^2 - 5x + 21x + 35
Combine the x^2's
7x^2 - 13x + 4 - 5x + 21x + 35
Combine the x's
7x^2 + 3x + 4 + 35
Combine the numbers without x's
7x^2 + 3x + 39