\((x+1)+(x+4)+(x+7)+...+(x+28)=195 \Rightarrow x+1+x+4+x+7+...+x+28=195\)

\(\Rightarrow 10x+(1+4+7+...+28)=195\)

\(\Rightarrow 10x+145=195\)

\(\Rightarrow 10x=50 \Rightarrow x = 5\)

\(60=2^2.3.5\)

\(90=2.3^2.5\)

\(135=3^3.5\)

\(\Rightarrow ƯCLN(60;90;135)=3.5=15\)

\((x+1) + (x+3) + ... + (x+99) = 3000 \Rightarrow x+1+x+3+...+x+99=3000\)

\(\Rightarrow 50x+(1+3+5+...+99)=3000\)

\(\Rightarrow 50x+2500=3000\)

\(\Rightarrow 50x = 500 \Rightarrow x = 10\)

1 When you game online, you be careful when make friends with strangers

2 We can see that Kim likes playing the piano

3 Some hobbies such as making crafts or collecting are interesting

4 Sitting in front of the computer all day can cause health problems

5 Do you fancy working with chilren?