1) 7x + 7y / 21 2) 8m-4n/4m 3) 9a+12b/3 4) 45c+18d/2d 5) 5x-xy/x 6) 6mn-4m/2m

7 х+7 у) / 21 = (7 (х+у)) / (7*3) = (х+у) / 3

(8m-4n) / 8m = (4 (2m-n)) / 4*2m = (2m-n) / 2m

(9a+12b) / 3 = (3 (3a+4b)) / 3=3a+4b

(45c+18d) / 27d = (9 (5c+2d)) / 9*3d = (5c+2d) / 3d

(5x-xy) / x=x (5-y) / x=5-y

(6mn-4m) / 2m = (2m (3n-1)) / 2m=3n-1