If there are x large panels, there are (9-x) small panels, depending on the conditions:

18x+ 10(9-x)= 130

18x+90- 10x = 130

8x= 130-90

x = 40 \8

x=5

9 x = 9 5 = 4

There are 5 large exhibition boards and 4 small exhibition boards.

Please adopt it if it is useful, but I don't know how to ask! !