脱式计算（1（5分之4—3分之2）*250%（2）2除以25分之4除以12分之5（3）8分之7—（0.5—25%）除以16分之7

(1) (4/5 - 2/3)×250% = (2/15) × (5/2) = 5/15 = 1/3
(2) 2÷(4/25)÷(5/12) = 2×(25/4)×(12/5) = (25/2)×(12/5) = 30
(3) 7/8 - (0.5 - 25%)÷(7/16) = 7/8 - (1/2 - 1/4)×(16/7)
= 7/8 - (1/4)×(16/7) = 7/8 - 4/7 = 17/56