to order these, it's easiest to find their decimal to better understand their value:
1/5 = 0.2
2/3 = 0.66666...
5/8 = 0.625
now order them from least to greatest. 0.2 is your smallest decimal here, followed by 0.625, and 0.66666 is last. change them back to fraction form: 1/5, 5/8, 2/3. this is the order from least to greatest.