Royal Sky

Chọn 1 hs trường A,sau đó chọn 1 trong 6 hs trg B ngồi đối diện vs hs đó
Học sinh thứ 2 trường A có 10 cách chọn ghế và 5 cách chọn hs trường B ngồi đối diện lại
Vậy có 12.6.10.5.8.4.6.3.4.2.2.1

Đặt số mol Fe và S là a và b
TH1: CT là MS
=>a=b và pt bảo toàn e giải đc a và b
Suy ra M+32=8,8/a
=>M=56
TH2:CT là MS2 làm tươg tự trên
Chắc thế

Bảo toàn e thôi

đây

Ex5: Arrange the words and phrases given in order to make meaningful sentences.

81-82. hours / boat / got / main / after / traveling / to / island / three / by / the / we //.

83-84. language centre / would like / about / and / interested / your / information / I / learning / some / I / in / am / English //.

85-86. wanted / clearly / the front line / the President / we / so / to see / stood / in / we.

87-88. people / mountain resorts / some rest / hard-working / many / go to / to have / a / after / week.

89-90. the sun / the roof / solar panels / on / of / the energy / installed / a house / from / are / to receive.

Ex6: Rewrite each of the following sentences in such a way that it means the same as the sentence printed before it. Use the bold words given in brackets. Do not alter the given words in any way. 

91-92. Because of his illness he could not work effectively. (IMPOSSIBLE)

93-94. Would you like to join our local drama group? (INTERESTED)

95-96. I was about to go out for dinner when he phoned. (POINT)

97-98. Would you rather I stayed with you during the holidays? (PREFER)

99-100. It rained continuously but we all enjoyed the trip. (IN SPITE OF)