20*2x-6x= 136

The solution is x=4.

4+2*4= 12 questions

A: This set of papers has a *** 12 question.

2、

1000 sets * * * available: 1000÷4=250 pieces.

Freight: 25*500*0.8= 10000 yuan.

Total cost:1000 * 26+10000 = 36,000 yuan.

Sales with 30% profit: 36,000 * (1+30%) = 46,800 yuan.

Completed sales quantity: 1000*( 1-20%)=800 sets.

Price per set: 46,800 ÷ 800 = 58.5 yuan.

A: It should be set at 58.5 yuan per set.