The factors of -21 that add up to 4 are 7 and -3, so put those as your two second values in your binomials and solve for x, in this case being the negative versions of the second term in the binomial
720 multiple by 25 gives you 18,000 then you find 25% of 18,000 by multiplying 18,000 times 25/100 which gives you 4,500. Or you can find 25%of 25 then multiple the answer by 720
