a) 3 rad 2 - 6 rad 2 + 7 rad 2 - 9 rad 2 = rad 2(3 - 6 + 7 - 9) = -5 rad 2
b) 4 rad 6 - 11 rad 6 - 10 rad 6 + 8 rad 6 = rad 6(4-11-10+8) = -9 rad 6
c) rad 24 - rad 96 + rad 54 - rad 150 = rad(2^3x3) - rad (2^5x3) + rad (2x3^3) - rad (2x3x5^2) = 2 rad 6 - 4 rad 6 + 3 rad 6 - 5 rad 6 = rad 6(2-4+3-5) = -4 rad 6