4x (x-8) - 5x (x-7) = -4 original line
4x^2 - 32x - (5x^2 - 35x) = -4 multiply out the two brackets with the outside of the brackets
4x^2 -32x - 5x^2 + 35x = -4 take out the second bracket fully by timesing by negative (swapping signs)
-x^2 +3x +4 = 0 gathering all terms together and adding 4 to both sides
(-x+4) (x+1) factorising.
x= -4 or x=-1 as each bracket must =0. Could also complete the square or use the quadratic formula if you know how, you will get the same answer though.