1/3x+1/5x+1/6x=21/40 1/4x+1/6x+1/8x=39/56 помогите пожалуста

1/3х + 1/5х + 1/6х = 21/40 10/30х + 6/30х + 5/30х = 21/40 21/30х = 21/40 7/10х = 21/40 28/40х = 21/40 х = 21/40 : 28/40 х = 21/40 * 40/28 х = 21/28 1/4х + 1/6х + 1/8х = 39/56 6/24х + 4/24х + 3/8х = 39/56 13/24х = 39/56 х = 39/56 : 13/24 х = 39/56 * 24/13 х = (3 * 24)/56 х = 72/56 = 9/7 = 1 2/7