用递等式计算（注意简算）25+19÷89-38849÷[98×（18+37）]（309×17+375）÷843.35×6.4×2+6.7×3.6．

Question

用递等式计算（注意简算）
(2)/(5)+(1)/(9)÷(8)/(9)-(3)/(8)
(8)/(49)÷[(9)/(8)×（(1)/(8)+(3)/(7)）]
（309×17+375）÷84
3.35×6.4×2+6.7×3.6．

Answer 1

(2)/(5)+(1)/(9)÷(8)/(9)-(3)/(8)
=(2)/(5)+(1)/(8)−(3)/(8)
=(16+5−15)/(40)
=(6)/(40)
=(3)/(20)；
(8)/(49)÷[(9)/(8)×（(1)/(8)+(3)/(7)）]
=(8)/(49)÷（(9)/(8)×(31)/(56)）
=(8)/(49)×(448)/(279)
=(3584)/(13671)；
（309×17+375）÷84
=（5253+375）÷84
=5628÷84
=67；
3.35×6.4×2+6.7×3.6
=6.7×6.4+6.7×3.6
=（6.4+3.6）×6.7
=10×6.7
=67．