Question 355236
Let paint required for 1 chair is x, and for table y.


so, 1 can = 3x = 2y  


or x = 2y/3 ...(1)


now, using 7 can is enough for 3*7 = 21 chairs = 12x+ 9x


here we have to convert 9x into terms of y using (1)


9x =  9 * (2y/3)

= 6y 


so, answer is 6 tables.