4u of tables and 5u of chairs → 120 - 44
= 76 (made of wood)

x 2 : 8u of tables and 10u of chairs
= 76 x 2 = 152

5u of tables and 2u of chairs = 44 (made of metal)

X 5 : 25u of tables and 10u of chairs
= 44 x 5
= 220


Difference = 220 - 152 = 68
→(25u - 8u) of tables
= 17u of tables

1u of tables = 68 ÷ 17 = 4

Tables made of wood = 4u
= 4 x 4
= 16

May I know why have to x2 : 8u tables and 10u chairs?

The idea is to make both sides have the same number of chairs (that is, 10u of chairs. one side has 2u and the other has 5u. The lowest common multiple is 10u)

So you can then compare the difference in the number of tables and find out how many tables make up 1 unit

Thank you very much.

Welcome

Sorry, I have another doubt. Does it mean I can use 4t 5c : 76 to cross multiply with 9t 7c : 120 or
5t 2c : 44 cross multiply with 9t 7c : 120??

Up to you. Both will work and you will get to the same answer. Try it!

Thank you for your clear and helpful explanation.