4) 4b/a^2+ab+b^2 = 4b(a-b)/(a-b)(a^2+ab+b^2)=4ab-4b^2/a^3-b^3
5) 9y/y-b=-9y/-(y-b)=-9y/b-y
6) -5x/x-10=5x/-(x-10)=5x/10-x
7) -4p/p+2=-4p(p-2)/(p-2)(p+2)=-4p^2+8p/p^2-4=-(-4p^2+8p)/-(p^2-4)=4p^2-8p/4-p^2
80 * 2^(-3) - 2^2 = 80 / (2^3) - 4 = 80 / 8 - 4 = 10 - 4 = 6