You can always try a Venn Diagram approach.

]]>can help me to check if my premises are correct?? how do u prove it?thanks alot

1) Every1 shouts or cries. not every1 cries. hence , some pple shout and dun cry.

is this correct?

S(x): x shouts

C(x): x cries

∀x(S(x) -> C(x))

∃x(~C(x))

thus. ∃x(S(x) ^ ~C(x))

2) All problems are difficult and frustrating. some problems are challenging. therefore some problems are challenging and frustrating.

D(x): x is difficult

F(x): x is frustrating

P(x): x is problem

C(x): x is challenging

how shld i approach this qns?

∀x(P(x) -> D(x) ^ F(x))

∃x(P(x) ^ C(x))

thus ∃x(C(x) ^ F(x))