To solve the first equation:

0.8x + 1.4 = 0.4x - 2.6

Subtract 0.4x from both sides:

0.4x + 1.4 = -2.6

Subtract 1.4 from both sides:

0.4x = -4

Divide by 0.4:

x = -10

To solve the second equation:

0.18x - 3.54 = 0.19x - 2.89

Subtract 0.18x from both sides:

-3.54 = 0.01x - 2.89

Add 2.89 to both sides:

-0.65 = 0.01x

Divide by 0.01:

x = -65

To solve the third equation:

2 2/3x + 3 2/15 = 3 1/5x + 2 1/3

Convert mixed numbers to improper fractions:

8/3x + 47/15 = 16/5x + 7/3

Subtract 8/3x from both sides:

47/15 = 16/5x - 8/3

Find a common denominator and simplify:

94/30 = 96/30x - 40/30

54/30 = 96/30x

Divide by 96/30:

x = 54/30 = 9/5