To find the value of x in each equation, we will need to isolate x by performing the necessary operations.

(2/5 + x) - 2/3 = 4/5

First, we need to simplify the left side of the equation:

2/5 + x - 2/3 = 4/5
(2/5 - 2/3) + x = 4/5
[(6/15) - (10/15)] + x = 4/5
(-4/15) + x = 4/5

Next, we isolate x by adding 4/15 to both sides:

x = 4/5 + 4/15
x = (12/15) + (4/15)
x = 16/15

Therefore, x = 16/15

x/90 - 2/13 = 8/45

First, we simplify the left side of the equation:

x/90 - 2/13 = 8/45
13x/1170 - 180/1170 = 208/1170
(13x - 180)/1170 = 208/1170

Next, we isolate x by multiplying both sides by 1170:

13x - 180 = 208
13x = 208 + 180
13x = 388
x = 388/13
x = 29.846

Therefore, x ≈ 29.846

(x - 3/14) + 2/7 = 5/6

First, we simplify the left side of the equation:

(x - 3/14) + 2/7 = 5/6
x - 3/14 + 2/7 = 5/6
x - 3/14 + 4/14 = 5/6
x + 1/14 = 5/6

Next, isolate x by subtracting 1/14 from both sides:

x = 5/6 - 1/14
x = (35/42) - (3/42)
x = 32/42
x = 16/21

Therefore, x = 16/21