2/3 + 0.6 = 2/3 + 2/3 = 4/3 = 1 1/3
2 1/4 - 1.7 = 9/4 - 1.7 = 9/4 - 1.7 = 2.25 - 1.7 = 0.55
1.5 ÷ 3/2 = 1.5 x 2/3 = 3/2 = 1.5 x 2/3 = 3/2 = 3/2 = 1.5

Поэтому результаты:
1) 2/3 + 0.6 = 1 1/3
2) 2 1/4 - 1.7 = 0.55
3) 1.5 ÷ 3/2 = 1.5