Question 794678
I'll give help on part (a).


The cost for x roses along with all the other expenses is:
{{{0.5x+60}}}


The revenue for selling x roses is {{{1.30x}}}.  


"Break even" means the revenue and the cost are equal.  You would want to then solve for the number of roses, x.  I am assuming something here, which is not exactly what the original question should have intended, that the students are buying as many roses as they sell.  


{{{0.5x+60=1.30x}}}
{{{(1.3-0.5)x=60}}}
{{{x=60/0.8}}}
{{{x=75}}} roses