7) (4 1/5 : x + 1 1/3) : 2 4/35 - 4/5 = 1 8/15;

(4 1/5 : x + 1 1/3) : 2 4/35 - 4/5 = (21/5 : x + 4/3) : 74/35 - 4/5 = (21/5 : x + 4/3) : 74/35 - 28/35 = (21/5 : x + 4/3) : 46/35 = 1 8/15 = 23/15. Therefore, 21/5 : x + 4/3 = (23/15) * (46/35) = 1058/525, 21/5 : x = 1058/525 - 4/3 = (1058 - 700)/525 = 358/525, x = (21/5) : (358/525) = (21/5) * (525/358) = 2205/1790 = 441/358.