(10 4/3-х)-5 11/13=3 7/13

(10 4 / 13 -x ) - 5  11/13 = 3  7/13
10 4/13 -x - 5 11/13 = 3  7/13
9  17/13 -x - 5 11/13 = 3  7/13
4  6/13 - x = 3  7/13
x = 4  6/13 - 3  7/13
x = 3  19/13 - 3 7/13
x = 12/13