To factor the trinomial, you can use the ac method where you multiply the first and last terms together (6 and 9) and add up to 15.
In this case ac= 54
2 numbers that multiply to 54 and add up to 15 would be 6 and 9 so place these numbers where the 15 would be:

Then group terms to simplify:

Simplify any like terms:

And group together again:

You can simplify a 3 out of the first expression one more time to get:

Which would be the factored form. I hope this helps :)
It equals 5,800. Good Luck In School!
4t+2c=200
2t+7c=400
I will solve for c in terms of t first
4t+2c=200
2c=200-4t
c=100-2t
Then I will substitute this in for c in the second equation to make it single variable
2t+7c=400
2t+7(100-2t)=400
2t+700-14t=400
300t=12
t=25
Tables cost $25 each
Plug t back into one of the ORIGINAL equations to find the cost of chairs
4(25)+2c=200
100+2c=200
2c=100
c=50
Chairs cost $50 each
Hope this helps! :)