0.9-（0.15+0.35÷5/7）
=0.9-(0.15+0.35×7/5)
=0.9-(0.15+0.49)
=0.9-0.64
=0.26
4/9x[3/4-(7/16-1/4)]
=4/9×[3/4-7/16+1/4]
=4/9×(1-7/16)
=4/9×9/16
=1/4
5/4x3/5÷3/2x2/3
=3/4÷3/2×2/3
=1/2×2/3
=1/3
[800+(280-240÷3)]-250
=800+280-80-250
=800+200-250
=750
999x222+333x334
=333×(666+334)
=333×1000
=333000