Question 161109
Let X be the number of dozen he bought.
Then (X-5) is the number of dozen he sold.

{{{Profit = Sales - Cost}}}
{{{18 = 2(X-5) - 1.5(X) }}}
{{{18 = 2X - 10 - 1.5X}}}
{{{28 = 0.5X}}}
{{{56 = X }}}
He bought 56 dozen and sold 51 of them.

That's a lot of flowers and not a lot of profit :(