Question 1018639
First you need to recognize that to break even means that R(t) = C(t). 
Therefore, let 120t = 40t + 700 and then solve for t as follows. 
120t = 40t + 700
120t - 40t = 700
80t = 700
t = 700 / 80
t = 8.75 
In other words, you would need to sell 8.75 tablecloths to break even. That means you need to sell at least 9 tablecloths to make a profit.