The original price of shirts in 20 yuan is 50% higher than that of trousers: 20× 50% =10 yuan;

Then, subtract this 10 yuan from Uncle Wang's 136 yuan,136-10 =126 yuan.

You can use shirts as pants, and this 126 yuan is equivalent to the original price of pants: (40%+50%).

So the original price of pants is:126 ÷ (40%+50%) =140 yuan.

The original price of the shirt is: 140+20= 160 yuan.