At $1.30 each you can guesstimate he'd have to sell almost 60 cones to break even. OR You can divide 1.30 into $61.00 for about 47 cones to break even. (I rounded up)
To make a profit he would either need to sell double that amount or he could raise the cost of his cone to $2.00 & make profit sooner.
We use the fact that x2+y2=1 This is the equation of the unit circle. We know that x=-4/5, so plug this in and solve for y x2+y2=1 <span>(−4/5)^2+y2=1</span> 16/25+y2=1 y2=1−16/25 y2=9/25 <span>y=−square root of 9/ 25</span> y = -3/5