Based on the problem statement you can write two equations for the cost of tables (t) and chairs (c).
.. 6c +2t = 20
.. 3c +5t = 35
You can solve these by your favorite method to find the costs are
.. chairs cost $1.25
.. tables cost $6.25
_____
My favorite method is to use the graphing calculator at Desmos [dot] com. Many graphing calculators will solve equations like these either directly, graphically, or indirectly using matrix functions. If you want to solve them by "elimination," you can double the second equation and subtract the first to get
.. 8t = 50