1, let ∠ABC=2a, ∠ACE=2b, ∠D=x, then we can see ∠A+2a=2b, ∠D+a=b, so ∠D equals ∠. An = a/2 n can be proved in the same way. So a5 = 3.

I can't imagine what it looks like.

I can't imagine what it looks like.

4. Add the two formulas to get B+C/2=P+A/2, D+A/2=P+C/2, and P=(B+D)/2.

I can't imagine what it looks like.

6. Suppose it's a day's work. Suppose there are X groups of workers producing tables and Y groups of workers producing chairs, then there are 2x groups of workers producing tables and 3y groups of workers producing chairs, 2x+3y = 28；; A group can produce 3 tables a day, 10 chairs and 4 chairs correspond to 1 table, so 3x*4= 10y. Available, x=5, y=6.