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謝謝

暫時淨係諗到a part

(28+34-42)/2=10

即係18個Ocean Park, 24個Space Museum, 10個both

OuS=O+S-OnS
42-7=28+34-OnS
OnS=27

a. 20 (OP x8 ; both x20 ; SM x14)
b. 27

回上面我無sol
聽日我番學校問下老師再覆您地啦

A) Set both to the S.P and O.M student is X,
X+42=28+34
X=20
So at least 20 students both to the S.P and O.M.

B) As 7 students have not been to the O.M or S.P,so just have 42-7=35 students must go to O.P or S.P or both.
As 35 students must go to O.P OR S.P OR both and just only 34 students go to S.P,so have 1 student JUST go to O.P,the other student of O.P MUST go to BOTH of them.
So 28-1=27 students have been to S.P and O.M

PS.我平時讀開中文班MATH,英文文法有錯請見諒 & thank for"brianlhm" c-hing remind

tommychow0811 :A) Set both to the S.P and O.M student is X,
X+42=28+34
X=20
So at least 20 students both to the S.P and O.M.

B) As 7 students have not been to the O.M or S.P,so just have 42-7=35 students must go to O.P or S.P or both.
As 35 students must go to O.P OR S.P OR both and just only 34 students go to S.P,so have 1 student have not been to S.P and the other student must go to S.P and O.M .
So 35-1=34 students have been to S.P and O.M

PS.我平時讀開中文班MATH,英文文法有錯請見諒

題目話有28個去過OP
如果你咁計,有34去過OP同SM
咁咪唔岩

brianlhm :

tommychow0811 :A) Set both to the S.P and O.M student is X,
X+42=28+34
X=20
So at least 20 students both to the S.P and O.M.

B) As 7 students have not been to the O.M or S.P,so just have 42-7=35 students must go to O.P or S.P or both.
As 35 students must go to O.P OR S.P OR both and just only 34 students go to S.P,so have 1 student have not been to S.P and the other student must go to S.P and O.M .
So 35-1=34 students have been to S.P and O.M

PS.我平時讀開中文班MATH,英文文法有錯請見諒

題目話有28個去過OP
如果你咁計,有34去過OP同SM
咁咪唔岩

sor,一時手快打錯野,我開頭都係唸係28-1先唸,我一路Organize 我d rubbish 英文而唔記得返d數點計=o="

多謝樓上咁多位解釋
答案真係20同7